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	$245.64	4.356%	$256.3401	$256.34	$256.35	$256.30
Purchase #2	$135.61	12.538%	$152.6128	$152.61	$152.60	$152.60
Purchase #3	$61.65	9.113%	$67.2682	$67.27	$67.25	$67.30
Purchase #4	$146.65	13.824%	$166.9229	$166.92	$166.90	$166.90
Purchase #5	$228.73	6.532%	$243.6706	$243.67	$243.65	$243.70
Purchase #6	$185.65	12.186%	$208.2733	$208.27	$208.25	$208.30
Purchase #7	$56.89	10.519%	$62.8743	$62.87	$62.85	$62.90
7 purchase totals =	$1,060.82		$1,157.9622	$1,157.95	$1,157.85	$1,158.00