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	$66.48	4.681%	$69.5919	$69.59	$69.60	$69.60
Purchase #2	$211.82	9.805%	$232.589	$232.59	$232.60	$232.60
Purchase #3	$138.59	5.650%	$146.4203	$146.42	$146.40	$146.40
Purchase #4	$212.45	12.212%	$238.3944	$238.39	$238.40	$238.40
Purchase #5	$231.66	9.435%	$253.5171	$253.52	$253.50	$253.50
Purchase #6	$127.25	3.409%	$131.588	$131.59	$131.60	$131.60
Purchase #7	$21.91	3.115%	$22.5925	$22.59	$22.60	$22.60
7 purchase totals =	$1,010.16		$1,094.6932	$1,094.69	$1,094.70	$1,094.70