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	$57.95	7.128%	$62.0807	$62.08	$62.10	$62.10
Purchase #2	$116.56	13.860%	$132.7152	$132.72	$132.70	$132.70
Purchase #3	$147.54	11.862%	$165.0412	$165.04	$165.05	$165.00
Purchase #4	$70.26	4.573%	$73.473	$73.47	$73.45	$73.50
Purchase #5	$42.90	5.190%	$45.1265	$45.13	$45.15	$45.10
Purchase #6	$62.52	3.214%	$64.5294	$64.53	$64.55	$64.50
Purchase #7	$45.97	10.634%	$50.8584	$50.86	$50.85	$50.90
7 purchase totals =	$543.70		$593.8244	$593.83	$593.85	$593.80