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	$49.67	7.709%	$53.4991	$53.50	$53.50	$53.50
Purchase #2	$153.69	3.802%	$159.5333	$159.53	$159.55	$159.50
Purchase #3	$195.74	7.605%	$210.626	$210.63	$210.65	$210.60
Purchase #4	$196.94	3.133%	$203.1101	$203.11	$203.10	$203.10
Purchase #5	$170.35	5.729%	$180.1094	$180.11	$180.10	$180.10
Purchase #6	$61.49	8.862%	$66.9392	$66.94	$66.95	$66.90
Purchase #7	$56.72	5.527%	$59.8549	$59.85	$59.85	$59.90
7 purchase totals =	$884.60		$933.6720	$933.67	$933.70	$933.60