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	$52.67	12.375%	$59.1879	$59.19	$59.20	$59.20
Purchase #2	$249.55	12.346%	$280.3594	$280.36	$280.35	$280.40
Purchase #3	$44.69	8.112%	$48.3153	$48.32	$48.30	$48.30
Purchase #4	$173.73	9.767%	$190.6982	$190.70	$190.70	$190.70
Purchase #5	$125.55	5.455%	$132.3988	$132.40	$132.40	$132.40
Purchase #6	$81.47	5.371%	$85.8458	$85.85	$85.85	$85.80
Purchase #7	$89.63	10.130%	$98.7095	$98.71	$98.70	$98.70
7 purchase totals =	$817.29		$895.5149	$895.53	$895.50	$895.50