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	$108.37	9.392%	$118.5481	$118.55	$118.55	$118.50
Purchase #2	$59.88	12.747%	$67.5129	$67.51	$67.50	$67.50
Purchase #3	$176.65	8.565%	$191.7801	$191.78	$191.80	$191.80
Purchase #4	$175.68	7.136%	$188.2165	$188.22	$188.20	$188.20
Purchase #5	$157.81	11.744%	$176.3432	$176.34	$176.35	$176.30
Purchase #6	$200.39	10.530%	$221.4911	$221.49	$221.50	$221.50
Purchase #7	$123.28	5.754%	$130.3735	$130.37	$130.35	$130.40
7 purchase totals =	$1,002.06		$1,094.2654	$1,094.26	$1,094.25	$1,094.20