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	$95.58	9.543%	$104.7012	$104.70	$104.70	$104.70
Purchase #2	$204.62	5.857%	$216.6046	$216.60	$216.60	$216.60
Purchase #3	$239.38	4.637%	$250.4801	$250.48	$250.50	$250.50
Purchase #4	$130.76	12.375%	$146.9416	$146.94	$146.95	$146.90
Purchase #5	$136.51	13.859%	$155.4289	$155.43	$155.45	$155.40
Purchase #6	$54.77	11.136%	$60.8692	$60.87	$60.85	$60.90
Purchase #7	$122.89	6.831%	$131.2846	$131.28	$131.30	$131.30
7 purchase totals =	$984.51		$1,066.3102	$1,066.30	$1,066.35	$1,066.30