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	$58.41	12.120%	$65.4893	$65.49	$65.50	$65.50
Purchase #2	$109.75	11.442%	$122.3076	$122.31	$122.30	$122.30
Purchase #3	$53.80	3.409%	$55.634	$55.63	$55.65	$55.60
Purchase #4	$50.61	7.708%	$54.511	$54.51	$54.50	$54.50
Purchase #5	$199.95	4.666%	$209.2797	$209.28	$209.30	$209.30
Purchase #6	$153.48	9.528%	$168.1036	$168.10	$168.10	$168.10
Purchase #7	$86.64	9.851%	$95.1749	$95.17	$95.15	$95.20
7 purchase totals =	$712.64		$770.5001	$770.49	$770.50	$770.50