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	$168.33	4.309%	$175.5833	$175.58	$175.60	$175.60
Purchase #2	$184.53	11.386%	$205.5406	$205.54	$205.55	$205.50
Purchase #3	$73.70	10.733%	$81.6102	$81.61	$81.60	$81.60
Purchase #4	$175.86	6.679%	$187.6057	$187.61	$187.60	$187.60
Purchase #5	$125.59	7.369%	$134.8447	$134.84	$134.85	$134.80
Purchase #6	$18.67	9.568%	$20.4563	$20.46	$20.45	$20.50
Purchase #7	$219.52	10.204%	$241.9198	$241.92	$241.90	$241.90
7 purchase totals =	$966.20		$1,047.5606	$1,047.56	$1,047.55	$1,047.50