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	$51.98	4.105%	$54.1138	$54.11	$54.10	$54.10
Purchase #2	$223.35	4.421%	$233.2243	$233.22	$233.20	$233.20
Purchase #3	$34.62	11.220%	$38.5044	$38.50	$38.50	$38.50
Purchase #4	$139.87	6.858%	$149.4623	$149.46	$149.45	$149.50
Purchase #5	$121.71	4.698%	$127.4279	$127.43	$127.45	$127.40
Purchase #6	$174.89	8.830%	$190.3328	$190.33	$190.35	$190.30
Purchase #7	$130.64	3.268%	$134.9093	$134.91	$134.90	$134.90
7 purchase totals =	$877.06		$927.9748	$927.96	$927.95	$927.90