Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$236.28	10.670%	$261.4911	$261.49	$261.50	$261.50
Purchase #2	$246.90	3.646%	$255.902	$255.90	$255.90	$255.90
Purchase #3	$203.29	9.343%	$222.2834	$222.28	$222.30	$222.30
Purchase #4	$162.67	3.427%	$168.2447	$168.24	$168.25	$168.20
Purchase #5	$118.81	10.868%	$131.7223	$131.72	$131.70	$131.70
Purchase #6	$95.62	4.391%	$99.8187	$99.82	$99.80	$99.80
Purchase #7	$23.39	6.441%	$24.8965	$24.90	$24.90	$24.90
7 purchase totals =	$1,086.96		$1,164.3587	$1,164.35	$1,164.35	$1,164.30