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	$176.35	12.213%	$197.8876	$197.89	$197.90	$197.90
Purchase #2	$146.53	8.430%	$158.8825	$158.88	$158.90	$158.90
Purchase #3	$116.71	12.412%	$131.196	$131.20	$131.20	$131.20
Purchase #4	$118.73	5.414%	$125.158	$125.16	$125.15	$125.20
Purchase #5	$219.95	13.363%	$249.3419	$249.34	$249.35	$249.30
Purchase #6	$147.69	9.827%	$162.2035	$162.20	$162.20	$162.20
Purchase #7	$232.96	9.843%	$255.8903	$255.89	$255.90	$255.90
7 purchase totals =	$1,158.92		$1,280.5598	$1,280.56	$1,280.60	$1,280.60