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	$50.58	4.452%	$52.8318	$52.83	$52.85	$52.80
Purchase #2	$34.50	5.585%	$36.4268	$36.43	$36.45	$36.40
Purchase #3	$127.95	12.838%	$144.3762	$144.38	$144.40	$144.40
Purchase #4	$223.31	6.625%	$238.1043	$238.10	$238.10	$238.10
Purchase #5	$144.41	10.140%	$159.0532	$159.05	$159.05	$159.10
Purchase #6	$205.55	8.259%	$222.5264	$222.53	$222.55	$222.50
Purchase #7	$98.61	6.114%	$104.639	$104.64	$104.65	$104.60
7 purchase totals =	$884.91		$957.9577	$957.96	$958.05	$957.90