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	$40.96	10.709%	$45.3464	$45.35	$45.35	$45.30
Purchase #2	$13.89	11.190%	$15.4443	$15.44	$15.45	$15.40
Purchase #3	$137.37	7.666%	$147.9008	$147.90	$147.90	$147.90
Purchase #4	$203.47	12.753%	$229.4185	$229.42	$229.40	$229.40
Purchase #5	$225.32	8.466%	$244.3956	$244.40	$244.40	$244.40
Purchase #6	$192.32	9.441%	$210.4769	$210.48	$210.50	$210.50
Purchase #7	$219.94	4.752%	$230.3915	$230.39	$230.40	$230.40
7 purchase totals =	$1,033.27		$1,123.3740	$1,123.38	$1,123.40	$1,123.30