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	$180.28	7.680%	$194.1255	$194.13	$194.15	$194.10
Purchase #2	$5.43	12.720%	$6.1207	$6.12	$6.10	$6.10
Purchase #3	$187.75	12.288%	$210.8207	$210.82	$210.80	$210.80
Purchase #4	$62.79	13.746%	$71.4211	$71.42	$71.40	$71.40
Purchase #5	$222.73	13.802%	$253.4712	$253.47	$253.45	$253.50
Purchase #6	$177.76	8.295%	$192.5052	$192.51	$192.50	$192.50
Purchase #7	$229.69	11.809%	$256.8141	$256.81	$256.80	$256.80
7 purchase totals =	$1,066.43		$1,185.2785	$1,185.28	$1,185.20	$1,185.20