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	$225.35	7.770%	$242.8597	$242.86	$242.85	$242.90
Purchase #2	$50.95	6.338%	$54.1792	$54.18	$54.20	$54.20
Purchase #3	$130.51	9.707%	$143.1786	$143.18	$143.20	$143.20
Purchase #4	$245.64	7.713%	$264.5862	$264.59	$264.60	$264.60
Purchase #5	$220.37	12.486%	$247.8854	$247.89	$247.90	$247.90
Purchase #6	$101.66	10.516%	$112.3506	$112.35	$112.35	$112.40
Purchase #7	$136.48	11.105%	$151.6361	$151.64	$151.65	$151.60
7 purchase totals =	$1,110.96		$1,216.6758	$1,216.69	$1,216.75	$1,216.80