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	$172.73	6.618%	$184.1613	$184.16	$184.15	$184.20
Purchase #2	$73.58	6.634%	$78.4613	$78.46	$78.45	$78.50
Purchase #3	$72.88	4.597%	$76.2303	$76.23	$76.25	$76.20
Purchase #4	$179.68	13.496%	$203.9296	$203.93	$203.95	$203.90
Purchase #5	$115.50	10.624%	$127.7707	$127.77	$127.75	$127.80
Purchase #6	$90.99	4.529%	$95.1109	$95.11	$95.10	$95.10
Purchase #7	$119.81	10.746%	$132.6848	$132.68	$132.70	$132.70
7 purchase totals =	$825.17		$898.3489	$898.34	$898.35	$898.40