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	$191.42	13.800%	$217.836	$217.84	$217.85	$217.80
Purchase #2	$147.66	3.290%	$152.518	$152.52	$152.50	$152.50
Purchase #3	$197.82	5.538%	$208.7753	$208.78	$208.80	$208.80
Purchase #4	$140.27	7.564%	$150.88	$150.88	$150.90	$150.90
Purchase #5	$191.72	13.849%	$218.2713	$218.27	$218.25	$218.30
Purchase #6	$199.81	6.853%	$213.503	$213.50	$213.50	$213.50
Purchase #7	$96.77	9.323%	$105.7919	$105.79	$105.80	$105.80
7 purchase totals =	$1,165.47		$1,267.5755	$1,267.58	$1,267.60	$1,267.60