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	$50.93	6.614%	$54.2985	$54.30	$54.30	$54.30
Purchase #2	$236.55	4.549%	$247.3107	$247.31	$247.30	$247.30
Purchase #3	$169.85	13.577%	$192.9105	$192.91	$192.90	$192.90
Purchase #4	$95.39	6.810%	$101.8861	$101.89	$101.90	$101.90
Purchase #5	$190.50	9.519%	$208.6337	$208.63	$208.65	$208.60
Purchase #6	$149.77	10.700%	$165.7954	$165.80	$165.80	$165.80
Purchase #7	$146.88	12.662%	$165.4779	$165.48	$165.50	$165.50
7 purchase totals =	$1,039.87		$1,136.3128	$1,136.32	$1,136.35	$1,136.30