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	$69.56	4.753%	$72.8662	$72.87	$72.85	$72.90
Purchase #2	$77.86	3.379%	$80.4909	$80.49	$80.50	$80.50
Purchase #3	$213.63	4.266%	$222.7435	$222.74	$222.75	$222.70
Purchase #4	$125.59	9.369%	$137.3565	$137.36	$137.35	$137.40
Purchase #5	$57.53	4.152%	$59.9186	$59.92	$59.90	$59.90
Purchase #6	$210.80	9.779%	$231.4141	$231.41	$231.40	$231.40
Purchase #7	$125.74	12.294%	$141.1985	$141.20	$141.20	$141.20
7 purchase totals =	$880.71		$945.9883	$945.99	$945.95	$946.00