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	$170.31	4.456%	$177.899	$177.90	$177.90	$177.90
Purchase #2	$90.30	3.708%	$93.6483	$93.65	$93.65	$93.60
Purchase #3	$121.46	7.435%	$130.4906	$130.49	$130.50	$130.50
Purchase #4	$89.78	6.803%	$95.8877	$95.89	$95.90	$95.90
Purchase #5	$137.83	10.156%	$151.828	$151.83	$151.85	$151.80
Purchase #6	$6.31	8.479%	$6.845	$6.85	$6.85	$6.80
Purchase #7	$247.37	13.502%	$280.7699	$280.77	$280.75	$280.80
7 purchase totals =	$863.36		$937.3685	$937.38	$937.40	$937.30