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	$130.39	13.129%	$147.5089	$147.51	$147.50	$147.50
Purchase #2	$83.96	11.814%	$93.879	$93.88	$93.90	$93.90
Purchase #3	$163.47	5.589%	$172.6063	$172.61	$172.60	$172.60
Purchase #4	$65.55	8.411%	$71.0634	$71.06	$71.05	$71.10
Purchase #5	$155.33	9.230%	$169.667	$169.67	$169.65	$169.70
Purchase #6	$195.89	13.145%	$221.6397	$221.64	$221.65	$221.60
Purchase #7	$144.66	7.738%	$155.8538	$155.85	$155.85	$155.90
7 purchase totals =	$939.25		$1,032.2181	$1,032.22	$1,032.20	$1,032.30