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	$225.87	9.513%	$247.357	$247.36	$247.35	$247.40
Purchase #2	$232.39	4.769%	$243.4727	$243.47	$243.45	$243.50
Purchase #3	$94.35	12.695%	$106.3277	$106.33	$106.35	$106.30
Purchase #4	$244.61	13.444%	$277.4954	$277.50	$277.50	$277.50
Purchase #5	$44.59	13.218%	$50.4839	$50.48	$50.50	$50.50
Purchase #6	$83.35	10.258%	$91.9	$91.90	$91.90	$91.90
Purchase #7	$41.80	5.617%	$44.1479	$44.15	$44.15	$44.10
7 purchase totals =	$966.96		$1,061.1846	$1,061.19	$1,061.20	$1,061.20