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	$57.44	9.222%	$62.7371	$62.74	$62.75	$62.70
Purchase #2	$158.76	5.137%	$166.9155	$166.92	$166.90	$166.90
Purchase #3	$132.63	12.135%	$148.7247	$148.72	$148.70	$148.70
Purchase #4	$173.60	8.198%	$187.8317	$187.83	$187.85	$187.80
Purchase #5	$204.77	8.800%	$222.7898	$222.79	$222.80	$222.80
Purchase #6	$123.57	3.309%	$127.6589	$127.66	$127.65	$127.70
Purchase #7	$36.96	5.305%	$38.9207	$38.92	$38.90	$38.90
7 purchase totals =	$887.73		$955.5784	$955.58	$955.55	$955.50