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	$112.83	11.419%	$125.7141	$125.71	$125.70	$125.70
Purchase #2	$56.75	13.498%	$64.4101	$64.41	$64.40	$64.40
Purchase #3	$152.51	6.829%	$162.9249	$162.92	$162.90	$162.90
Purchase #4	$209.33	6.458%	$222.8485	$222.85	$222.85	$222.80
Purchase #5	$143.25	11.323%	$159.4702	$159.47	$159.45	$159.50
Purchase #6	$70.57	11.197%	$78.4717	$78.47	$78.45	$78.50
Purchase #7	$10.49	6.235%	$11.1441	$11.14	$11.15	$11.10
7 purchase totals =	$755.73		$824.9836	$824.97	$824.90	$824.90