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	$116.31	6.232%	$123.5584	$123.56	$123.55	$123.60
Purchase #2	$232.62	4.155%	$242.2854	$242.29	$242.30	$242.30
Purchase #3	$19.30	5.302%	$20.3233	$20.32	$20.30	$20.30
Purchase #4	$234.49	9.578%	$256.9495	$256.95	$256.95	$256.90
Purchase #5	$203.58	4.707%	$213.1625	$213.16	$213.15	$213.20
Purchase #6	$67.38	12.853%	$76.0404	$76.04	$76.05	$76.00
Purchase #7	$152.82	5.545%	$161.2939	$161.29	$161.30	$161.30
7 purchase totals =	$1,026.50		$1,093.6134	$1,093.61	$1,093.60	$1,093.60