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	$193.43	12.472%	$217.5546	$217.55	$217.55	$217.60
Purchase #2	$33.25	8.445%	$36.058	$36.06	$36.05	$36.10
Purchase #3	$81.60	12.282%	$91.6221	$91.62	$91.60	$91.60
Purchase #4	$136.85	10.832%	$151.6736	$151.67	$151.65	$151.70
Purchase #5	$93.46	7.706%	$100.662	$100.66	$100.65	$100.70
Purchase #6	$165.59	12.233%	$185.8466	$185.85	$185.85	$185.80
Purchase #7	$247.59	3.780%	$256.9489	$256.95	$256.95	$256.90
7 purchase totals =	$951.77		$1,040.3658	$1,040.36	$1,040.30	$1,040.40