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	$86.54	11.680%	$96.6479	$96.65	$96.65	$96.60
Purchase #2	$73.44	6.517%	$78.2261	$78.23	$78.25	$78.20
Purchase #3	$13.61	13.536%	$15.4522	$15.45	$15.45	$15.50
Purchase #4	$119.65	5.445%	$126.1649	$126.16	$126.15	$126.20
Purchase #5	$10.81	11.678%	$12.0724	$12.07	$12.05	$12.10
Purchase #6	$152.51	11.359%	$169.8336	$169.83	$169.85	$169.80
Purchase #7	$52.53	11.427%	$58.5326	$58.53	$58.55	$58.50
7 purchase totals =	$509.09		$556.9297	$556.92	$556.95	$556.90