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	$43.47	11.804%	$48.6012	$48.60	$48.60	$48.60
Purchase #2	$166.89	5.223%	$175.6067	$175.61	$175.60	$175.60
Purchase #3	$231.71	8.293%	$250.9257	$250.93	$250.95	$250.90
Purchase #4	$43.58	6.144%	$46.2576	$46.26	$46.25	$46.30
Purchase #5	$21.75	11.458%	$24.2421	$24.24	$24.25	$24.20
Purchase #6	$50.73	7.708%	$54.6403	$54.64	$54.65	$54.60
Purchase #7	$195.47	13.481%	$221.8213	$221.82	$221.80	$221.80
7 purchase totals =	$753.60		$822.0949	$822.10	$822.10	$822.00