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	$203.56	6.407%	$216.6021	$216.60	$216.60	$216.60
Purchase #2	$76.42	7.198%	$81.9207	$81.92	$81.90	$81.90
Purchase #3	$214.43	13.531%	$243.4445	$243.44	$243.45	$243.40
Purchase #4	$11.61	5.385%	$12.2352	$12.24	$12.25	$12.20
Purchase #5	$137.25	8.353%	$148.7145	$148.71	$148.70	$148.70
Purchase #6	$159.60	13.301%	$180.8284	$180.83	$180.85	$180.80
Purchase #7	$147.85	7.266%	$158.5928	$158.59	$158.60	$158.60
7 purchase totals =	$950.72		$1,042.3382	$1,042.33	$1,042.35	$1,042.20