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	$233.95	8.874%	$254.7107	$254.71	$254.70	$254.70
Purchase #2	$44.99	11.505%	$50.1661	$50.17	$50.15	$50.20
Purchase #3	$229.33	9.437%	$250.9719	$250.97	$250.95	$251.00
Purchase #4	$78.98	9.682%	$86.6268	$86.63	$86.65	$86.60
Purchase #5	$38.74	10.378%	$42.7604	$42.76	$42.75	$42.80
Purchase #6	$249.89	7.872%	$269.5613	$269.56	$269.55	$269.60
Purchase #7	$151.94	13.369%	$172.2529	$172.25	$172.25	$172.30
7 purchase totals =	$1,027.82		$1,127.0501	$1,127.05	$1,127.00	$1,127.20