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	$111.86	13.579%	$127.0495	$127.05	$127.05	$127.00
Purchase #2	$72.34	13.548%	$82.1406	$82.14	$82.15	$82.10
Purchase #3	$105.34	5.204%	$110.8219	$110.82	$110.80	$110.80
Purchase #4	$145.89	7.663%	$157.0696	$157.07	$157.05	$157.10
Purchase #5	$198.85	11.153%	$221.0277	$221.03	$221.05	$221.00
Purchase #6	$110.35	8.264%	$119.4693	$119.47	$119.45	$119.50
Purchase #7	$10.38	13.585%	$11.7901	$11.79	$11.80	$11.80
7 purchase totals =	$755.01		$829.3687	$829.37	$829.35	$829.30