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	$101.27	11.235%	$112.6477	$112.65	$112.65	$112.60
Purchase #2	$21.72	11.750%	$24.2721	$24.27	$24.25	$24.30
Purchase #3	$249.42	12.668%	$281.0165	$281.02	$281.00	$281.00
Purchase #4	$48.83	11.444%	$54.4181	$54.42	$54.40	$54.40
Purchase #5	$22.33	11.484%	$24.8944	$24.89	$24.90	$24.90
Purchase #6	$245.47	12.385%	$275.8715	$275.87	$275.85	$275.90
Purchase #7	$193.57	8.167%	$209.3789	$209.38	$209.40	$209.40
7 purchase totals =	$882.61		$982.4992	$982.50	$982.45	$982.50