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	$130.90	13.448%	$148.5034	$148.50	$148.50	$148.50
Purchase #2	$169.84	11.312%	$189.0523	$189.05	$189.05	$189.10
Purchase #3	$244.86	12.663%	$275.8666	$275.87	$275.85	$275.90
Purchase #4	$227.99	12.594%	$256.7031	$256.70	$256.70	$256.70
Purchase #5	$189.80	4.536%	$198.4093	$198.41	$198.40	$198.40
Purchase #6	$198.77	11.862%	$222.3481	$222.35	$222.35	$222.30
Purchase #7	$198.60	6.196%	$210.9053	$210.91	$210.90	$210.90
7 purchase totals =	$1,360.76		$1,501.7881	$1,501.79	$1,501.75	$1,501.80