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	$180.77	4.146%	$188.2647	$188.26	$188.25	$188.30
Purchase #2	$138.72	4.250%	$144.6156	$144.62	$144.60	$144.60
Purchase #3	$143.73	4.630%	$150.3847	$150.38	$150.40	$150.40
Purchase #4	$41.53	4.168%	$43.261	$43.26	$43.25	$43.30
Purchase #5	$113.46	9.586%	$124.3363	$124.34	$124.35	$124.30
Purchase #6	$83.32	12.213%	$93.4959	$93.50	$93.50	$93.50
Purchase #7	$132.99	13.800%	$151.3426	$151.34	$151.35	$151.30
7 purchase totals =	$834.52		$895.7008	$895.70	$895.70	$895.70