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	$211.93	12.400%	$238.2093	$238.21	$238.20	$238.20
Purchase #2	$224.52	6.202%	$238.4447	$238.44	$238.45	$238.40
Purchase #3	$11.50	13.362%	$13.0366	$13.04	$13.05	$13.00
Purchase #4	$156.89	9.705%	$172.1162	$172.12	$172.10	$172.10
Purchase #5	$128.81	6.649%	$137.3746	$137.37	$137.35	$137.40
Purchase #6	$132.75	4.672%	$138.9521	$138.95	$138.95	$139.00
Purchase #7	$100.73	7.780%	$108.5668	$108.57	$108.55	$108.60
7 purchase totals =	$967.13		$1,046.7003	$1,046.70	$1,046.65	$1,046.70