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	$117.25	12.768%	$132.2205	$132.22	$132.20	$132.20
Purchase #2	$211.84	7.273%	$227.2471	$227.25	$227.25	$227.20
Purchase #3	$85.88	3.661%	$89.0241	$89.02	$89.00	$89.00
Purchase #4	$236.66	6.411%	$251.8323	$251.83	$251.85	$251.80
Purchase #5	$86.28	7.700%	$92.9236	$92.92	$92.90	$92.90
Purchase #6	$104.72	9.326%	$114.4862	$114.49	$114.50	$114.50
Purchase #7	$83.62	6.848%	$89.3463	$89.35	$89.35	$89.30
7 purchase totals =	$926.25		$997.0801	$997.08	$997.05	$996.90