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	$93.89	12.273%	$105.4131	$105.41	$105.40	$105.40
Purchase #2	$209.50	10.632%	$231.774	$231.77	$231.75	$231.80
Purchase #3	$146.37	11.768%	$163.5948	$163.59	$163.60	$163.60
Purchase #4	$250.37	10.440%	$276.5086	$276.51	$276.50	$276.50
Purchase #5	$235.88	5.860%	$249.7026	$249.70	$249.70	$249.70
Purchase #6	$95.54	10.217%	$105.3013	$105.30	$105.30	$105.30
Purchase #7	$117.82	4.492%	$123.1125	$123.11	$123.10	$123.10
7 purchase totals =	$1,149.37		$1,255.4069	$1,255.39	$1,255.35	$1,255.40