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	$135.34	13.403%	$153.4796	$153.48	$153.50	$153.50
Purchase #2	$206.38	4.798%	$216.2821	$216.28	$216.30	$216.30
Purchase #3	$43.82	8.356%	$47.4816	$47.48	$47.50	$47.50
Purchase #4	$50.25	12.520%	$56.5413	$56.54	$56.55	$56.50
Purchase #5	$95.41	5.420%	$100.5812	$100.58	$100.60	$100.60
Purchase #6	$134.95	5.610%	$142.5207	$142.52	$142.50	$142.50
Purchase #7	$159.42	10.375%	$175.9598	$175.96	$175.95	$176.00
7 purchase totals =	$825.57		$892.8463	$892.84	$892.90	$892.90