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	$58.64	5.267%	$61.7286	$61.73	$61.75	$61.70
Purchase #2	$41.74	8.634%	$45.3438	$45.34	$45.35	$45.30
Purchase #3	$36.46	9.256%	$39.8347	$39.83	$39.85	$39.80
Purchase #4	$112.46	13.348%	$127.4712	$127.47	$127.45	$127.50
Purchase #5	$219.38	4.557%	$229.3771	$229.38	$229.40	$229.40
Purchase #6	$14.95	8.489%	$16.2191	$16.22	$16.20	$16.20
Purchase #7	$55.86	8.219%	$60.4511	$60.45	$60.45	$60.50
7 purchase totals =	$539.49		$580.4256	$580.42	$580.45	$580.40