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	$119.61	10.166%	$131.7696	$131.77	$131.75	$131.80
Purchase #2	$89.26	9.630%	$97.8557	$97.86	$97.85	$97.90
Purchase #3	$245.52	6.260%	$260.8896	$260.89	$260.90	$260.90
Purchase #4	$144.86	11.535%	$161.5696	$161.57	$161.55	$161.60
Purchase #5	$29.89	10.152%	$32.9244	$32.92	$32.90	$32.90
Purchase #6	$22.86	8.682%	$24.8447	$24.84	$24.85	$24.80
Purchase #7	$44.98	12.822%	$50.7473	$50.75	$50.75	$50.70
7 purchase totals =	$696.98		$760.6009	$760.60	$760.55	$760.60