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	$208.43	11.770%	$232.9622	$232.96	$232.95	$233.00
Purchase #2	$210.28	9.550%	$230.3617	$230.36	$230.35	$230.40
Purchase #3	$140.32	4.317%	$146.3776	$146.38	$146.40	$146.40
Purchase #4	$84.45	4.337%	$88.1126	$88.11	$88.10	$88.10
Purchase #5	$40.89	10.336%	$45.1164	$45.12	$45.10	$45.10
Purchase #6	$63.69	12.484%	$71.6411	$71.64	$71.65	$71.60
Purchase #7	$104.64	6.335%	$111.2689	$111.27	$111.25	$111.30
7 purchase totals =	$852.70		$925.8405	$925.84	$925.80	$925.90