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	$41.25	11.290%	$45.9071	$45.91	$45.90	$45.90
Purchase #2	$56.89	7.862%	$61.3627	$61.36	$61.35	$61.40
Purchase #3	$53.97	10.171%	$59.4593	$59.46	$59.45	$59.50
Purchase #4	$49.93	12.418%	$56.1303	$56.13	$56.15	$56.10
Purchase #5	$6.37	12.206%	$7.1475	$7.15	$7.15	$7.10
Purchase #6	$52.63	8.782%	$57.252	$57.25	$57.25	$57.30
Purchase #7	$152.35	9.277%	$166.4835	$166.48	$166.50	$166.50
7 purchase totals =	$413.39		$453.7424	$453.74	$453.75	$453.80