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	$181.49	8.115%	$196.2179	$196.22	$196.20	$196.20
Purchase #2	$231.77	13.121%	$262.1805	$262.18	$262.20	$262.20
Purchase #3	$131.37	10.244%	$144.8275	$144.83	$144.85	$144.80
Purchase #4	$135.34	4.390%	$141.2814	$141.28	$141.30	$141.30
Purchase #5	$130.53	12.434%	$146.7601	$146.76	$146.75	$146.80
Purchase #6	$179.36	11.726%	$200.3918	$200.39	$200.40	$200.40
Purchase #7	$226.25	11.152%	$251.4814	$251.48	$251.50	$251.50
7 purchase totals =	$1,216.11		$1,343.1406	$1,343.14	$1,343.20	$1,343.20