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	$181.73	13.513%	$206.2872	$206.29	$206.30	$206.30
Purchase #2	$152.33	3.231%	$157.2518	$157.25	$157.25	$157.30
Purchase #3	$23.64	3.105%	$24.374	$24.37	$24.35	$24.40
Purchase #4	$203.43	9.480%	$222.7152	$222.72	$222.70	$222.70
Purchase #5	$35.60	6.832%	$38.0322	$38.03	$38.05	$38.00
Purchase #6	$225.56	13.758%	$256.5925	$256.59	$256.60	$256.60
Purchase #7	$69.40	4.165%	$72.2905	$72.29	$72.30	$72.30
7 purchase totals =	$891.69		$977.5434	$977.54	$977.55	$977.60