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	$94.77	11.212%	$105.3956	$105.40	$105.40	$105.40
Purchase #2	$207.94	13.726%	$236.4818	$236.48	$236.50	$236.50
Purchase #3	$54.52	9.813%	$59.87	$59.87	$59.85	$59.90
Purchase #4	$116.96	3.420%	$120.96	$120.96	$120.95	$121.00
Purchase #5	$134.89	10.457%	$148.9954	$149.00	$149.00	$149.00
Purchase #6	$105.89	6.369%	$112.6341	$112.63	$112.65	$112.60
Purchase #7	$206.50	10.306%	$227.7819	$227.78	$227.80	$227.80
7 purchase totals =	$921.47		$1,012.1188	$1,012.12	$1,012.15	$1,012.20