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	$87.42	13.615%	$99.3222	$99.32	$99.30	$99.30
Purchase #2	$223.96	12.140%	$251.1487	$251.15	$251.15	$251.10
Purchase #3	$14.44	3.636%	$14.965	$14.97	$14.95	$15.00
Purchase #4	$152.55	10.463%	$168.5113	$168.51	$168.50	$168.50
Purchase #5	$143.48	6.510%	$152.8205	$152.82	$152.80	$152.80
Purchase #6	$76.41	11.811%	$85.4348	$85.43	$85.45	$85.40
Purchase #7	$228.61	10.865%	$253.4485	$253.45	$253.45	$253.40
7 purchase totals =	$926.87		$1,025.6510	$1,025.65	$1,025.60	$1,025.50