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	$207.39	7.319%	$222.5689	$222.57	$222.55	$222.60
Purchase #2	$247.67	6.718%	$264.3085	$264.31	$264.30	$264.30
Purchase #3	$138.94	13.587%	$157.8178	$157.82	$157.80	$157.80
Purchase #4	$43.35	4.767%	$45.4165	$45.42	$45.40	$45.40
Purchase #5	$236.91	3.170%	$244.42	$244.42	$244.40	$244.40
Purchase #6	$141.81	7.746%	$152.7946	$152.79	$152.80	$152.80
Purchase #7	$12.42	10.378%	$13.7089	$13.71	$13.70	$13.70
7 purchase totals =	$1,028.49		$1,101.0352	$1,101.04	$1,100.95	$1,101.00