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	$32.82	10.664%	$36.3199	$36.32	$36.30	$36.30
Purchase #2	$231.40	6.866%	$247.2879	$247.29	$247.30	$247.30
Purchase #3	$123.58	6.151%	$131.1814	$131.18	$131.20	$131.20
Purchase #4	$80.56	8.390%	$87.319	$87.32	$87.30	$87.30
Purchase #5	$93.42	13.231%	$105.7804	$105.78	$105.80	$105.80
Purchase #6	$245.70	9.801%	$269.7811	$269.78	$269.80	$269.80
Purchase #7	$198.55	5.555%	$209.5795	$209.58	$209.60	$209.60
7 purchase totals =	$1,006.03		$1,087.2492	$1,087.25	$1,087.30	$1,087.30