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	$228.62	7.456%	$245.6659	$245.67	$245.65	$245.70
Purchase #2	$173.53	4.195%	$180.8096	$180.81	$180.80	$180.80
Purchase #3	$81.79	8.115%	$88.4273	$88.43	$88.45	$88.40
Purchase #4	$38.74	9.383%	$42.375	$42.38	$42.40	$42.40
Purchase #5	$53.93	11.145%	$59.9405	$59.94	$59.95	$59.90
Purchase #6	$166.62	3.651%	$172.7033	$172.70	$172.70	$172.70
Purchase #7	$38.97	6.434%	$41.4773	$41.48	$41.50	$41.50
7 purchase totals =	$782.20		$831.3989	$831.41	$831.45	$831.40