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	$120.95	8.392%	$131.1001	$131.10	$131.10	$131.10
Purchase #2	$66.79	6.823%	$71.3471	$71.35	$71.35	$71.30
Purchase #3	$131.58	9.863%	$144.5577	$144.56	$144.55	$144.60
Purchase #4	$6.76	13.535%	$7.675	$7.68	$7.70	$7.70
Purchase #5	$39.62	7.537%	$42.6062	$42.61	$42.60	$42.60
Purchase #6	$141.96	8.554%	$154.1033	$154.10	$154.10	$154.10
Purchase #7	$169.62	12.388%	$190.6325	$190.63	$190.65	$190.60
7 purchase totals =	$677.28		$742.0219	$742.03	$742.05	$742.00