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	$232.37	10.371%	$256.4691	$256.47	$256.45	$256.50
Purchase #2	$177.37	4.684%	$185.678	$185.68	$185.70	$185.70
Purchase #3	$127.62	4.360%	$133.1842	$133.18	$133.20	$133.20
Purchase #4	$63.85	11.698%	$71.3192	$71.32	$71.30	$71.30
Purchase #5	$63.64	12.309%	$71.4734	$71.47	$71.45	$71.50
Purchase #6	$59.57	7.816%	$64.226	$64.23	$64.25	$64.20
Purchase #7	$83.41	11.596%	$93.0822	$93.08	$93.10	$93.10
7 purchase totals =	$807.83		$875.4321	$875.43	$875.45	$875.50