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	$227.52	13.437%	$258.0919	$258.09	$258.10	$258.10
Purchase #2	$220.77	4.863%	$231.506	$231.51	$231.50	$231.50
Purchase #3	$93.73	7.449%	$100.7119	$100.71	$100.70	$100.70
Purchase #4	$210.34	8.743%	$228.73	$228.73	$228.75	$228.70
Purchase #5	$101.43	5.377%	$106.8839	$106.88	$106.90	$106.90
Purchase #6	$73.89	7.618%	$79.5189	$79.52	$79.50	$79.50
Purchase #7	$82.88	12.139%	$92.9408	$92.94	$92.95	$92.90
7 purchase totals =	$1,010.56		$1,098.3834	$1,098.38	$1,098.40	$1,098.30