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	$213.88	3.864%	$222.1443	$222.14	$222.15	$222.10
Purchase #2	$229.92	9.578%	$251.9417	$251.94	$251.95	$251.90
Purchase #3	$250.44	13.191%	$283.4755	$283.48	$283.50	$283.50
Purchase #4	$175.33	11.396%	$195.3106	$195.31	$195.30	$195.30
Purchase #5	$46.86	6.246%	$49.7869	$49.79	$49.80	$49.80
Purchase #6	$179.51	11.680%	$200.4768	$200.48	$200.50	$200.50
Purchase #7	$212.65	13.172%	$240.6603	$240.66	$240.65	$240.70
7 purchase totals =	$1,308.59		$1,443.7961	$1,443.80	$1,443.85	$1,443.80