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	$198.83	6.413%	$211.581	$211.58	$211.60	$211.60
Purchase #2	$158.67	7.460%	$170.5068	$170.51	$170.50	$170.50
Purchase #3	$41.52	3.734%	$43.0704	$43.07	$43.05	$43.10
Purchase #4	$21.38	4.242%	$22.2869	$22.29	$22.30	$22.30
Purchase #5	$197.56	12.672%	$222.5948	$222.59	$222.60	$222.60
Purchase #6	$166.74	12.712%	$187.936	$187.94	$187.95	$187.90
Purchase #7	$169.81	13.505%	$192.7428	$192.74	$192.75	$192.70
7 purchase totals =	$954.51		$1,050.7187	$1,050.72	$1,050.75	$1,050.70