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	$47.25	7.240%	$50.6709	$50.67	$50.65	$50.70
Purchase #2	$169.72	13.150%	$192.0382	$192.04	$192.05	$192.00
Purchase #3	$50.78	13.289%	$57.5282	$57.53	$57.55	$57.50
Purchase #4	$53.92	13.529%	$61.2148	$61.21	$61.20	$61.20
Purchase #5	$216.70	10.508%	$239.4708	$239.47	$239.45	$239.50
Purchase #6	$69.89	3.676%	$72.4592	$72.46	$72.45	$72.50
Purchase #7	$82.83	7.403%	$88.9619	$88.96	$88.95	$89.00
7 purchase totals =	$691.09		$762.3440	$762.34	$762.30	$762.40