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	$54.83	12.196%	$61.5171	$61.52	$61.50	$61.50
Purchase #2	$151.42	9.125%	$165.2371	$165.24	$165.25	$165.20
Purchase #3	$155.59	8.438%	$168.7187	$168.72	$168.70	$168.70
Purchase #4	$27.96	10.622%	$30.9299	$30.93	$30.95	$30.90
Purchase #5	$40.41	5.291%	$42.5481	$42.55	$42.55	$42.50
Purchase #6	$71.56	7.362%	$76.8282	$76.83	$76.85	$76.80
Purchase #7	$163.57	7.523%	$175.8754	$175.88	$175.90	$175.90
7 purchase totals =	$665.34		$721.6545	$721.67	$721.70	$721.50