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	$213.46	4.271%	$222.5769	$222.58	$222.60	$222.60
Purchase #2	$67.78	6.816%	$72.3999	$72.40	$72.40	$72.40
Purchase #3	$137.29	4.454%	$143.4049	$143.40	$143.40	$143.40
Purchase #4	$195.50	5.697%	$206.6376	$206.64	$206.65	$206.60
Purchase #5	$89.82	6.413%	$95.5802	$95.58	$95.60	$95.60
Purchase #6	$88.84	7.155%	$95.1965	$95.20	$95.20	$95.20
Purchase #7	$145.37	11.774%	$162.4859	$162.49	$162.50	$162.50
7 purchase totals =	$938.06		$998.2819	$998.29	$998.35	$998.30