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	$104.92	11.624%	$117.1159	$117.12	$117.10	$117.10
Purchase #2	$246.43	12.283%	$276.699	$276.70	$276.70	$276.70
Purchase #3	$40.32	12.158%	$45.2221	$45.22	$45.20	$45.20
Purchase #4	$117.64	8.719%	$127.897	$127.90	$127.90	$127.90
Purchase #5	$72.63	7.501%	$78.078	$78.08	$78.10	$78.10
Purchase #6	$205.84	7.678%	$221.6444	$221.64	$221.65	$221.60
Purchase #7	$68.51	11.118%	$76.1269	$76.13	$76.15	$76.10
7 purchase totals =	$856.29		$942.7833	$942.79	$942.80	$942.70