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	$188.42	4.346%	$196.6087	$196.61	$196.60	$196.60
Purchase #2	$229.61	13.600%	$260.837	$260.84	$260.85	$260.80
Purchase #3	$40.32	6.227%	$42.8307	$42.83	$42.85	$42.80
Purchase #4	$67.97	4.773%	$71.2142	$71.21	$71.20	$71.20
Purchase #5	$214.58	7.151%	$229.9246	$229.92	$229.90	$229.90
Purchase #6	$235.94	6.674%	$251.6866	$251.69	$251.70	$251.70
Purchase #7	$29.85	13.803%	$33.9702	$33.97	$33.95	$34.00
7 purchase totals =	$1,006.69		$1,087.0720	$1,087.07	$1,087.05	$1,087.00