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	$88.29	12.243%	$99.0993	$99.10	$99.10	$99.10
Purchase #2	$43.62	3.314%	$45.0656	$45.07	$45.05	$45.10
Purchase #3	$175.85	8.294%	$190.435	$190.44	$190.45	$190.40
Purchase #4	$55.65	12.647%	$62.6881	$62.69	$62.70	$62.70
Purchase #5	$149.86	9.444%	$164.0128	$164.01	$164.00	$164.00
Purchase #6	$88.58	7.394%	$95.1296	$95.13	$95.15	$95.10
Purchase #7	$34.51	9.449%	$37.7708	$37.77	$37.75	$37.80
7 purchase totals =	$636.36		$694.2012	$694.21	$694.20	$694.20