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	$32.55	12.213%	$36.5253	$36.53	$36.55	$36.50
Purchase #2	$78.56	6.792%	$83.8958	$83.90	$83.90	$83.90
Purchase #3	$69.76	12.578%	$78.5344	$78.53	$78.55	$78.50
Purchase #4	$241.52	6.578%	$257.4072	$257.41	$257.40	$257.40
Purchase #5	$213.71	11.307%	$237.8742	$237.87	$237.85	$237.90
Purchase #6	$141.58	6.700%	$151.0659	$151.07	$151.05	$151.10
Purchase #7	$77.35	13.823%	$88.0421	$88.04	$88.05	$88.00
7 purchase totals =	$855.03		$933.3449	$933.35	$933.35	$933.30