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	$234.37	10.334%	$258.5898	$258.59	$258.60	$258.60
Purchase #2	$78.85	8.345%	$85.43	$85.43	$85.45	$85.40
Purchase #3	$23.59	5.527%	$24.8938	$24.89	$24.90	$24.90
Purchase #4	$129.34	12.290%	$145.2359	$145.24	$145.25	$145.20
Purchase #5	$98.27	8.733%	$106.8519	$106.85	$106.85	$106.90
Purchase #6	$106.91	11.448%	$119.1491	$119.15	$119.15	$119.10
Purchase #7	$149.71	3.782%	$155.372	$155.37	$155.35	$155.40
7 purchase totals =	$821.04		$895.5225	$895.52	$895.55	$895.50