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	$116.88	6.259%	$124.1955	$124.20	$124.20	$124.20
Purchase #2	$216.40	11.187%	$240.6087	$240.61	$240.60	$240.60
Purchase #3	$157.30	13.506%	$178.5449	$178.54	$178.55	$178.50
Purchase #4	$62.36	7.198%	$66.8487	$66.85	$66.85	$66.80
Purchase #5	$152.29	10.398%	$168.1251	$168.13	$168.15	$168.10
Purchase #6	$64.29	10.692%	$71.1639	$71.16	$71.15	$71.20
Purchase #7	$156.87	5.399%	$165.3394	$165.34	$165.35	$165.30
7 purchase totals =	$926.39		$1,014.8262	$1,014.83	$1,014.85	$1,014.70