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	$169.97	13.673%	$193.21	$193.21	$193.20	$193.20
Purchase #2	$247.74	4.738%	$259.4779	$259.48	$259.50	$259.50
Purchase #3	$223.85	11.866%	$250.412	$250.41	$250.40	$250.40
Purchase #4	$35.73	13.479%	$40.546	$40.55	$40.55	$40.50
Purchase #5	$70.40	10.729%	$77.9532	$77.95	$77.95	$78.00
Purchase #6	$158.83	9.490%	$173.903	$173.90	$173.90	$173.90
Purchase #7	$111.77	5.666%	$118.1029	$118.10	$118.10	$118.10
7 purchase totals =	$1,018.29		$1,113.6050	$1,113.60	$1,113.60	$1,113.60