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	$56.88	4.647%	$59.5232	$59.52	$59.50	$59.50
Purchase #2	$249.29	3.762%	$258.6683	$258.67	$258.65	$258.70
Purchase #3	$186.87	7.237%	$200.3938	$200.39	$200.40	$200.40
Purchase #4	$236.94	11.575%	$264.3658	$264.37	$264.35	$264.40
Purchase #5	$212.85	5.812%	$225.2208	$225.22	$225.20	$225.20
Purchase #6	$151.45	12.530%	$170.4267	$170.43	$170.45	$170.40
Purchase #7	$248.98	7.348%	$267.2751	$267.28	$267.30	$267.30
7 purchase totals =	$1,343.26		$1,445.8737	$1,445.88	$1,445.85	$1,445.90