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	$126.64	13.306%	$143.4907	$143.49	$143.50	$143.50
Purchase #2	$184.48	6.621%	$196.6944	$196.69	$196.70	$196.70
Purchase #3	$143.40	6.287%	$152.4156	$152.42	$152.40	$152.40
Purchase #4	$133.90	13.148%	$151.5052	$151.51	$151.50	$151.50
Purchase #5	$204.42	8.140%	$221.0598	$221.06	$221.05	$221.10
Purchase #6	$245.53	9.248%	$268.2366	$268.24	$268.25	$268.20
Purchase #7	$214.58	12.812%	$242.072	$242.07	$242.05	$242.10
7 purchase totals =	$1,252.95		$1,375.4743	$1,375.48	$1,375.45	$1,375.50