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	$240.82	5.520%	$254.1133	$254.11	$254.10	$254.10
Purchase #2	$25.43	11.132%	$28.2609	$28.26	$28.25	$28.30
Purchase #3	$85.51	5.473%	$90.19	$90.19	$90.20	$90.20
Purchase #4	$32.45	8.684%	$35.268	$35.27	$35.25	$35.30
Purchase #5	$239.50	10.384%	$264.3697	$264.37	$264.35	$264.40
Purchase #6	$222.73	13.326%	$252.411	$252.41	$252.40	$252.40
Purchase #7	$213.93	5.491%	$225.6769	$225.68	$225.70	$225.70
7 purchase totals =	$1,060.37		$1,150.2898	$1,150.29	$1,150.25	$1,150.40