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	$163.62	9.136%	$178.5683	$178.57	$178.55	$178.60
Purchase #2	$226.95	12.677%	$255.7205	$255.72	$255.70	$255.70
Purchase #3	$61.57	9.285%	$67.2868	$67.29	$67.30	$67.30
Purchase #4	$156.91	7.370%	$168.4743	$168.47	$168.45	$168.50
Purchase #5	$71.29	5.689%	$75.3457	$75.35	$75.35	$75.30
Purchase #6	$78.94	8.612%	$85.7383	$85.74	$85.75	$85.70
Purchase #7	$89.59	12.191%	$100.5119	$100.51	$100.50	$100.50
7 purchase totals =	$848.87		$931.6458	$931.65	$931.60	$931.60