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	$191.66	4.188%	$199.6867	$199.69	$199.70	$199.70
Purchase #2	$131.94	13.318%	$149.5118	$149.51	$149.50	$149.50
Purchase #3	$42.80	4.162%	$44.5813	$44.58	$44.60	$44.60
Purchase #4	$172.51	13.660%	$196.0749	$196.07	$196.05	$196.10
Purchase #5	$181.49	13.591%	$206.1563	$206.16	$206.15	$206.20
Purchase #6	$246.57	9.409%	$269.7698	$269.77	$269.75	$269.80
Purchase #7	$82.45	9.673%	$90.4254	$90.43	$90.45	$90.40
7 purchase totals =	$1,049.42		$1,156.2062	$1,156.21	$1,156.20	$1,156.30