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	$203.29	6.331%	$216.1603	$216.16	$216.15	$216.20
Purchase #2	$13.75	7.383%	$14.7652	$14.77	$14.75	$14.80
Purchase #3	$146.50	10.792%	$162.3103	$162.31	$162.30	$162.30
Purchase #4	$222.78	10.219%	$245.5459	$245.55	$245.55	$245.50
Purchase #5	$158.46	7.570%	$170.4554	$170.46	$170.45	$170.50
Purchase #6	$160.44	4.468%	$167.6085	$167.61	$167.60	$167.60
Purchase #7	$102.31	3.546%	$105.9379	$105.94	$105.95	$105.90
7 purchase totals =	$1,007.53		$1,082.7835	$1,082.80	$1,082.75	$1,082.80