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	$137.65	10.519%	$152.1294	$152.13	$152.15	$152.10
Purchase #2	$93.70	10.387%	$103.4326	$103.43	$103.45	$103.40
Purchase #3	$240.38	10.505%	$265.6319	$265.63	$265.65	$265.60
Purchase #4	$37.63	11.322%	$41.8905	$41.89	$41.90	$41.90
Purchase #5	$172.41	10.403%	$190.3458	$190.35	$190.35	$190.30
Purchase #6	$211.83	8.555%	$229.9521	$229.95	$229.95	$230.00
Purchase #7	$130.96	7.696%	$141.0387	$141.04	$141.05	$141.00
7 purchase totals =	$1,024.56		$1,124.4210	$1,124.42	$1,124.50	$1,124.30