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	$159.58	8.648%	$173.3805	$173.38	$173.40	$173.40
Purchase #2	$116.35	10.521%	$128.5912	$128.59	$128.60	$128.60
Purchase #3	$94.40	4.595%	$98.7377	$98.74	$98.75	$98.70
Purchase #4	$124.50	12.807%	$140.4447	$140.44	$140.45	$140.40
Purchase #5	$227.76	6.213%	$241.9107	$241.91	$241.90	$241.90
Purchase #6	$155.90	7.860%	$168.1537	$168.15	$168.15	$168.20
Purchase #7	$76.83	7.388%	$82.5062	$82.51	$82.50	$82.50
7 purchase totals =	$955.32		$1,033.7247	$1,033.72	$1,033.75	$1,033.70