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	$29.91	11.460%	$33.3377	$33.34	$33.35	$33.30
Purchase #2	$176.66	13.492%	$200.495	$200.50	$200.50	$200.50
Purchase #3	$107.33	11.317%	$119.4765	$119.48	$119.50	$119.50
Purchase #4	$202.66	10.255%	$223.4428	$223.44	$223.45	$223.40
Purchase #5	$100.55	5.265%	$105.844	$105.84	$105.85	$105.80
Purchase #6	$22.28	9.635%	$24.4267	$24.43	$24.45	$24.40
Purchase #7	$155.98	7.802%	$168.1496	$168.15	$168.15	$168.10
7 purchase totals =	$795.37		$875.1723	$875.18	$875.25	$875.00