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	$78.39	6.300%	$83.3286	$83.33	$83.35	$83.30
Purchase #2	$232.63	12.325%	$261.3016	$261.30	$261.30	$261.30
Purchase #3	$247.43	3.524%	$256.1494	$256.15	$256.15	$256.10
Purchase #4	$222.46	12.203%	$249.6068	$249.61	$249.60	$249.60
Purchase #5	$48.66	11.702%	$54.3542	$54.35	$54.35	$54.40
Purchase #6	$113.62	11.472%	$126.6545	$126.65	$126.65	$126.70
Purchase #7	$205.56	9.715%	$225.5302	$225.53	$225.55	$225.50
7 purchase totals =	$1,148.75		$1,256.9253	$1,256.92	$1,256.95	$1,256.90