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	$57.70	3.501%	$59.7201	$59.72	$59.70	$59.70
Purchase #2	$183.97	5.638%	$194.3422	$194.34	$194.35	$194.30
Purchase #3	$222.69	9.224%	$243.2309	$243.23	$243.25	$243.20
Purchase #4	$184.81	8.569%	$200.6464	$200.65	$200.65	$200.60
Purchase #5	$138.29	6.248%	$146.9304	$146.93	$146.95	$146.90
Purchase #6	$127.39	7.789%	$137.3124	$137.31	$137.30	$137.30
Purchase #7	$244.75	11.173%	$272.0959	$272.10	$272.10	$272.10
7 purchase totals =	$1,159.60		$1,254.2783	$1,254.28	$1,254.30	$1,254.10