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	$89.91	4.382%	$93.8499	$93.85	$93.85	$93.80
Purchase #2	$216.30	13.236%	$244.9295	$244.93	$244.95	$244.90
Purchase #3	$50.31	5.834%	$53.2451	$53.25	$53.25	$53.20
Purchase #4	$153.37	8.526%	$166.4463	$166.45	$166.45	$166.40
Purchase #5	$85.28	11.738%	$95.2902	$95.29	$95.30	$95.30
Purchase #6	$220.42	8.121%	$238.3203	$238.32	$238.30	$238.30
Purchase #7	$207.50	7.720%	$223.519	$223.52	$223.50	$223.50
7 purchase totals =	$1,023.09		$1,115.6003	$1,115.61	$1,115.60	$1,115.40