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	$123.33	5.863%	$130.5608	$130.56	$130.55	$130.60
Purchase #2	$236.92	12.276%	$266.0043	$266.00	$266.00	$266.00
Purchase #3	$241.81	9.829%	$265.5775	$265.58	$265.60	$265.60
Purchase #4	$215.94	4.467%	$225.586	$225.59	$225.60	$225.60
Purchase #5	$47.67	6.635%	$50.8329	$50.83	$50.85	$50.80
Purchase #6	$69.42	12.269%	$77.9371	$77.94	$77.95	$77.90
Purchase #7	$75.55	4.206%	$78.7276	$78.73	$78.75	$78.70
7 purchase totals =	$1,010.64		$1,095.2262	$1,095.23	$1,095.30	$1,095.20