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	$169.39	3.631%	$175.5406	$175.54	$175.55	$175.50
Purchase #2	$55.51	11.440%	$61.8603	$61.86	$61.85	$61.90
Purchase #3	$92.47	8.634%	$100.4539	$100.45	$100.45	$100.50
Purchase #4	$10.71	9.860%	$11.766	$11.77	$11.75	$11.80
Purchase #5	$237.40	7.819%	$255.9623	$255.96	$255.95	$256.00
Purchase #6	$68.51	4.621%	$71.6758	$71.68	$71.70	$71.70
Purchase #7	$95.64	5.476%	$100.8772	$100.88	$100.90	$100.90
7 purchase totals =	$729.63		$778.1361	$778.14	$778.15	$778.30