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	$52.38	9.532%	$57.3729	$57.37	$57.35	$57.40
Purchase #2	$141.25	5.437%	$148.9298	$148.93	$148.95	$148.90
Purchase #3	$210.35	13.331%	$238.3918	$238.39	$238.40	$238.40
Purchase #4	$227.31	7.161%	$243.5877	$243.59	$243.60	$243.60
Purchase #5	$144.89	5.225%	$152.4605	$152.46	$152.45	$152.50
Purchase #6	$62.28	11.547%	$69.4715	$69.47	$69.45	$69.50
Purchase #7	$239.43	7.225%	$256.7288	$256.73	$256.75	$256.70
7 purchase totals =	$1,077.89		$1,166.9430	$1,166.94	$1,166.95	$1,167.00