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	$147.84	13.362%	$167.5944	$167.59	$167.60	$167.60
Purchase #2	$176.59	8.378%	$191.3847	$191.38	$191.40	$191.40
Purchase #3	$9.38	12.129%	$10.5177	$10.52	$10.50	$10.50
Purchase #4	$233.50	6.726%	$249.2052	$249.21	$249.20	$249.20
Purchase #5	$214.52	6.254%	$227.9361	$227.94	$227.95	$227.90
Purchase #6	$7.29	13.581%	$8.2801	$8.28	$8.30	$8.30
Purchase #7	$37.67	7.573%	$40.5227	$40.52	$40.50	$40.50
7 purchase totals =	$826.79		$895.4409	$895.44	$895.45	$895.40