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	$153.56	6.589%	$163.6781	$163.68	$163.70	$163.70
Purchase #2	$146.47	13.308%	$165.9622	$165.96	$165.95	$166.00
Purchase #3	$163.27	10.769%	$180.8525	$180.85	$180.85	$180.90
Purchase #4	$73.45	6.496%	$78.2213	$78.22	$78.20	$78.20
Purchase #5	$72.86	11.175%	$81.0021	$81.00	$81.00	$81.00
Purchase #6	$196.58	6.619%	$209.5916	$209.59	$209.60	$209.60
Purchase #7	$64.87	10.828%	$71.8941	$71.89	$71.90	$71.90
7 purchase totals =	$871.06		$951.2019	$951.19	$951.20	$951.30