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	$161.48	8.205%	$174.7294	$174.73	$174.75	$174.70
Purchase #2	$248.58	4.706%	$260.2782	$260.28	$260.30	$260.30
Purchase #3	$88.34	11.196%	$98.2305	$98.23	$98.25	$98.20
Purchase #4	$198.47	13.565%	$225.3925	$225.39	$225.40	$225.40
Purchase #5	$200.80	11.416%	$223.7233	$223.72	$223.70	$223.70
Purchase #6	$111.29	4.779%	$116.6085	$116.61	$116.60	$116.60
Purchase #7	$22.59	10.745%	$25.0173	$25.02	$25.00	$25.00
7 purchase totals =	$1,031.55		$1,123.9797	$1,123.98	$1,124.00	$1,123.90