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	$183.98	6.237%	$195.4548	$195.45	$195.45	$195.50
Purchase #2	$151.49	7.252%	$162.4761	$162.48	$162.50	$162.50
Purchase #3	$43.90	6.675%	$46.8303	$46.83	$46.85	$46.80
Purchase #4	$72.94	12.580%	$82.1159	$82.12	$82.10	$82.10
Purchase #5	$247.26	11.163%	$274.8616	$274.86	$274.85	$274.90
Purchase #6	$183.64	13.849%	$209.0723	$209.07	$209.05	$209.10
Purchase #7	$94.53	5.169%	$99.4163	$99.42	$99.40	$99.40
7 purchase totals =	$977.74		$1,070.2273	$1,070.23	$1,070.20	$1,070.30