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	$156.72	9.487%	$171.588	$171.59	$171.60	$171.60
Purchase #2	$235.47	11.489%	$262.5231	$262.52	$262.50	$262.50
Purchase #3	$138.35	6.642%	$147.5392	$147.54	$147.55	$147.50
Purchase #4	$160.94	6.185%	$170.8941	$170.89	$170.90	$170.90
Purchase #5	$117.52	5.324%	$123.7768	$123.78	$123.80	$123.80
Purchase #6	$146.29	4.751%	$153.2402	$153.24	$153.25	$153.20
Purchase #7	$206.54	7.434%	$221.8942	$221.89	$221.90	$221.90
7 purchase totals =	$1,161.83		$1,251.4556	$1,251.45	$1,251.50	$1,251.40