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	$196.31	13.546%	$222.9022	$222.90	$222.90	$222.90
Purchase #2	$11.49	4.107%	$11.9619	$11.96	$11.95	$12.00
Purchase #3	$94.92	9.810%	$104.2317	$104.23	$104.25	$104.20
Purchase #4	$141.62	10.461%	$156.4349	$156.43	$156.45	$156.40
Purchase #5	$79.41	5.529%	$83.8006	$83.80	$83.80	$83.80
Purchase #6	$101.78	5.586%	$107.4654	$107.47	$107.45	$107.50
Purchase #7	$242.32	13.313%	$274.5801	$274.58	$274.60	$274.60
7 purchase totals =	$867.85		$961.3768	$961.37	$961.40	$961.40