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	$225.97	12.116%	$253.3485	$253.35	$253.35	$253.30
Purchase #2	$119.92	11.362%	$133.5453	$133.55	$133.55	$133.50
Purchase #3	$85.42	5.610%	$90.2121	$90.21	$90.20	$90.20
Purchase #4	$94.65	5.157%	$99.5311	$99.53	$99.55	$99.50
Purchase #5	$116.58	13.275%	$132.056	$132.06	$132.05	$132.10
Purchase #6	$246.89	12.506%	$277.7661	$277.77	$277.75	$277.80
Purchase #7	$126.44	8.251%	$136.8726	$136.87	$136.85	$136.90
7 purchase totals =	$1,015.87		$1,123.3317	$1,123.34	$1,123.30	$1,123.30