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	$194.78	4.328%	$203.2101	$203.21	$203.20	$203.20
Purchase #2	$197.38	13.290%	$223.6118	$223.61	$223.60	$223.60
Purchase #3	$104.66	6.323%	$111.2777	$111.28	$111.30	$111.30
Purchase #4	$112.26	9.767%	$123.2244	$123.22	$123.20	$123.20
Purchase #5	$232.36	8.217%	$251.453	$251.45	$251.45	$251.50
Purchase #6	$32.32	11.816%	$36.1389	$36.14	$36.15	$36.10
Purchase #7	$71.71	12.287%	$80.521	$80.52	$80.50	$80.50
7 purchase totals =	$945.47		$1,029.4369	$1,029.43	$1,029.40	$1,029.40