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	$90.87	5.426%	$95.8006	$95.80	$95.80	$95.80
Purchase #2	$7.76	8.789%	$8.442	$8.44	$8.45	$8.40
Purchase #3	$121.69	13.144%	$137.6849	$137.68	$137.70	$137.70
Purchase #4	$53.58	10.244%	$59.0687	$59.07	$59.05	$59.10
Purchase #5	$44.37	4.473%	$46.3547	$46.35	$46.35	$46.40
Purchase #6	$196.63	13.576%	$223.3245	$223.32	$223.30	$223.30
Purchase #7	$145.39	13.512%	$165.0351	$165.04	$165.05	$165.00
7 purchase totals =	$660.29		$735.7105	$735.70	$735.70	$735.70