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	$196.93	13.571%	$223.6554	$223.66	$223.65	$223.70
Purchase #2	$166.31	11.750%	$185.8514	$185.85	$185.85	$185.90
Purchase #3	$136.88	10.445%	$151.1771	$151.18	$151.20	$151.20
Purchase #4	$152.31	8.580%	$165.3782	$165.38	$165.40	$165.40
Purchase #5	$234.63	5.442%	$247.3986	$247.40	$247.40	$247.40
Purchase #6	$199.63	13.713%	$227.0053	$227.01	$227.00	$227.00
Purchase #7	$19.86	7.412%	$21.332	$21.33	$21.35	$21.30
7 purchase totals =	$1,106.55		$1,221.7980	$1,221.81	$1,221.85	$1,221.90