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	$127.25	3.184%	$131.3016	$131.30	$131.30	$131.30
Purchase #2	$36.89	8.361%	$39.9744	$39.97	$39.95	$40.00
Purchase #3	$83.81	11.321%	$93.2981	$93.30	$93.30	$93.30
Purchase #4	$166.41	11.366%	$185.3242	$185.32	$185.30	$185.30
Purchase #5	$62.36	7.602%	$67.1006	$67.10	$67.10	$67.10
Purchase #6	$223.72	4.281%	$233.2975	$233.30	$233.30	$233.30
Purchase #7	$182.73	12.828%	$206.1706	$206.17	$206.15	$206.20
7 purchase totals =	$883.17		$956.4670	$956.46	$956.40	$956.50