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	$194.62	13.768%	$221.4153	$221.42	$221.40	$221.40
Purchase #2	$230.33	6.738%	$245.8496	$245.85	$245.85	$245.80
Purchase #3	$37.69	6.160%	$40.0117	$40.01	$40.00	$40.00
Purchase #4	$60.66	11.196%	$67.4515	$67.45	$67.45	$67.50
Purchase #5	$245.87	7.319%	$263.8652	$263.87	$263.85	$263.90
Purchase #6	$28.70	13.862%	$32.6784	$32.68	$32.70	$32.70
Purchase #7	$250.59	5.161%	$263.5229	$263.52	$263.50	$263.50
7 purchase totals =	$1,048.46		$1,134.7946	$1,134.80	$1,134.75	$1,134.80