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	$100.47	4.184%	$104.6737	$104.67	$104.65	$104.70
Purchase #2	$16.87	8.141%	$18.2434	$18.24	$18.25	$18.20
Purchase #3	$189.61	11.408%	$211.2407	$211.24	$211.25	$211.20
Purchase #4	$56.97	5.667%	$60.1985	$60.20	$60.20	$60.20
Purchase #5	$207.31	6.615%	$221.0236	$221.02	$221.00	$221.00
Purchase #6	$70.45	11.392%	$78.4757	$78.48	$78.50	$78.50
Purchase #7	$229.54	11.363%	$255.6226	$255.62	$255.60	$255.60
7 purchase totals =	$871.22		$949.4782	$949.47	$949.45	$949.40