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	$103.82	7.207%	$111.3023	$111.30	$111.30	$111.30
Purchase #2	$38.45	6.268%	$40.86	$40.86	$40.85	$40.90
Purchase #3	$60.45	11.110%	$67.166	$67.17	$67.15	$67.20
Purchase #4	$40.27	12.872%	$45.4536	$45.45	$45.45	$45.50
Purchase #5	$65.30	9.732%	$71.655	$71.66	$71.65	$71.70
Purchase #6	$30.64	5.378%	$32.2878	$32.29	$32.30	$32.30
Purchase #7	$11.61	12.306%	$13.0387	$13.04	$13.05	$13.00
7 purchase totals =	$350.54		$381.7634	$381.77	$381.75	$381.90