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	$161.72	4.299%	$168.6723	$168.67	$168.65	$168.70
Purchase #2	$58.82	10.671%	$65.0967	$65.10	$65.10	$65.10
Purchase #3	$150.82	3.586%	$156.2284	$156.23	$156.25	$156.20
Purchase #4	$192.32	12.248%	$215.8754	$215.88	$215.90	$215.90
Purchase #5	$203.81	4.410%	$212.798	$212.80	$212.80	$212.80
Purchase #6	$192.57	13.361%	$218.2993	$218.30	$218.30	$218.30
Purchase #7	$17.84	4.268%	$18.6014	$18.60	$18.60	$18.60
7 purchase totals =	$977.90		$1,055.5715	$1,055.58	$1,055.60	$1,055.60