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	$91.64	13.856%	$104.3376	$104.34	$104.35	$104.30
Purchase #2	$68.61	6.164%	$72.8391	$72.84	$72.85	$72.80
Purchase #3	$12.75	3.579%	$13.2063	$13.21	$13.20	$13.20
Purchase #4	$38.35	5.709%	$40.5394	$40.54	$40.55	$40.50
Purchase #5	$24.26	3.181%	$25.0317	$25.03	$25.05	$25.00
Purchase #6	$138.95	6.128%	$147.4649	$147.46	$147.45	$147.50
Purchase #7	$39.98	5.471%	$42.1673	$42.17	$42.15	$42.20
7 purchase totals =	$414.54		$445.5863	$445.59	$445.60	$445.50