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	$196.56	13.123%	$222.3546	$222.35	$222.35	$222.40
Purchase #2	$180.30	5.698%	$190.5735	$190.57	$190.55	$190.60
Purchase #3	$97.28	8.299%	$105.3533	$105.35	$105.35	$105.40
Purchase #4	$82.93	9.551%	$90.8506	$90.85	$90.85	$90.90
Purchase #5	$169.44	6.440%	$180.3519	$180.35	$180.35	$180.40
Purchase #6	$10.50	5.588%	$11.0867	$11.09	$11.10	$11.10
Purchase #7	$172.96	10.266%	$190.7161	$190.72	$190.70	$190.70
7 purchase totals =	$909.97		$991.2867	$991.28	$991.25	$991.50