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	$174.50	7.111%	$186.9087	$186.91	$186.90	$186.90
Purchase #2	$75.30	13.818%	$85.705	$85.71	$85.70	$85.70
Purchase #3	$198.57	9.584%	$217.6009	$217.60	$217.60	$217.60
Purchase #4	$189.49	10.127%	$208.6797	$208.68	$208.70	$208.70
Purchase #5	$152.32	12.192%	$170.8909	$170.89	$170.90	$170.90
Purchase #6	$203.51	12.348%	$228.6394	$228.64	$228.65	$228.60
Purchase #7	$83.52	7.395%	$89.6963	$89.70	$89.70	$89.70
7 purchase totals =	$1,077.21		$1,188.1209	$1,188.13	$1,188.15	$1,188.10