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	$203.95	13.725%	$231.9421	$231.94	$231.95	$231.90
Purchase #2	$38.67	5.569%	$40.8235	$40.82	$40.80	$40.80
Purchase #3	$200.61	5.542%	$211.7278	$211.73	$211.75	$211.70
Purchase #4	$169.69	9.175%	$185.2591	$185.26	$185.25	$185.30
Purchase #5	$134.63	12.590%	$151.5799	$151.58	$151.60	$151.60
Purchase #6	$90.48	7.670%	$97.4198	$97.42	$97.40	$97.40
Purchase #7	$223.73	6.583%	$238.4581	$238.46	$238.45	$238.50
7 purchase totals =	$1,061.76		$1,157.2103	$1,157.21	$1,157.20	$1,157.20