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	$76.81	11.817%	$85.8866	$85.89	$85.90	$85.90
Purchase #2	$213.27	5.831%	$225.7058	$225.71	$225.70	$225.70
Purchase #3	$190.67	4.714%	$199.6582	$199.66	$199.65	$199.70
Purchase #4	$193.34	11.251%	$215.0927	$215.09	$215.10	$215.10
Purchase #5	$215.88	3.433%	$223.2912	$223.29	$223.30	$223.30
Purchase #6	$170.89	9.553%	$187.2151	$187.22	$187.20	$187.20
Purchase #7	$166.65	8.366%	$180.5919	$180.59	$180.60	$180.60
7 purchase totals =	$1,227.51		$1,317.4415	$1,317.45	$1,317.45	$1,317.50