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	$175.29	13.433%	$198.8367	$198.84	$198.85	$198.80
Purchase #2	$83.66	5.760%	$88.4788	$88.48	$88.50	$88.50
Purchase #3	$200.34	11.492%	$223.3631	$223.36	$223.35	$223.40
Purchase #4	$172.73	5.434%	$182.1161	$182.12	$182.10	$182.10
Purchase #5	$112.95	6.249%	$120.0082	$120.01	$120.00	$120.00
Purchase #6	$152.60	10.698%	$168.9251	$168.93	$168.95	$168.90
Purchase #7	$57.76	6.194%	$61.3377	$61.34	$61.35	$61.30
7 purchase totals =	$955.33		$1,043.0657	$1,043.08	$1,043.10	$1,043.00