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	$57.37	13.151%	$64.9147	$64.91	$64.90	$64.90
Purchase #2	$216.40	5.302%	$227.8735	$227.87	$227.85	$227.90
Purchase #3	$81.43	4.720%	$85.2735	$85.27	$85.25	$85.30
Purchase #4	$104.86	7.634%	$112.865	$112.87	$112.85	$112.90
Purchase #5	$212.31	8.136%	$229.5835	$229.58	$229.60	$229.60
Purchase #6	$101.63	12.273%	$114.103	$114.10	$114.10	$114.10
Purchase #7	$78.47	13.337%	$88.9355	$88.94	$88.95	$88.90
7 purchase totals =	$852.47		$923.5487	$923.54	$923.50	$923.60