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	$196.55	11.569%	$219.2889	$219.29	$219.30	$219.30
Purchase #2	$247.42	11.478%	$275.8189	$275.82	$275.80	$275.80
Purchase #3	$207.66	11.561%	$231.6676	$231.67	$231.65	$231.70
Purchase #4	$72.68	13.621%	$82.5797	$82.58	$82.60	$82.60
Purchase #5	$126.94	11.754%	$141.8605	$141.86	$141.85	$141.90
Purchase #6	$189.98	10.245%	$209.4435	$209.44	$209.45	$209.40
Purchase #7	$35.36	12.311%	$39.7132	$39.71	$39.70	$39.70
7 purchase totals =	$1,076.59		$1,200.3723	$1,200.37	$1,200.35	$1,200.40