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	$228.30	11.269%	$254.0271	$254.03	$254.05	$254.00
Purchase #2	$40.72	12.352%	$45.7497	$45.75	$45.75	$45.70
Purchase #3	$124.91	6.574%	$133.1216	$133.12	$133.10	$133.10
Purchase #4	$49.54	5.575%	$52.3019	$52.30	$52.30	$52.30
Purchase #5	$245.59	13.664%	$279.1474	$279.15	$279.15	$279.10
Purchase #6	$196.39	13.489%	$222.881	$222.88	$222.90	$222.90
Purchase #7	$154.37	11.849%	$172.6613	$172.66	$172.65	$172.70
7 purchase totals =	$1,039.82		$1,159.8900	$1,159.89	$1,159.90	$1,159.80