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	$158.87	8.871%	$172.9634	$172.96	$172.95	$173.00
Purchase #2	$11.78	7.369%	$12.6481	$12.65	$12.65	$12.60
Purchase #3	$164.42	7.423%	$176.6249	$176.62	$176.60	$176.60
Purchase #4	$45.40	11.689%	$50.7068	$50.71	$50.70	$50.70
Purchase #5	$33.64	11.618%	$37.5483	$37.55	$37.55	$37.50
Purchase #6	$111.37	10.484%	$123.046	$123.05	$123.05	$123.00
Purchase #7	$33.73	8.594%	$36.6288	$36.63	$36.65	$36.60
7 purchase totals =	$559.21		$610.1663	$610.17	$610.15	$610.00