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	$196.29	8.702%	$213.3712	$213.37	$213.35	$213.40
Purchase #2	$166.79	13.457%	$189.2349	$189.23	$189.25	$189.20
Purchase #3	$116.29	12.805%	$131.1809	$131.18	$131.20	$131.20
Purchase #4	$5.72	10.697%	$6.3319	$6.33	$6.35	$6.30
Purchase #5	$75.60	9.433%	$82.7313	$82.73	$82.75	$82.70
Purchase #6	$14.43	7.297%	$15.483	$15.48	$15.50	$15.50
Purchase #7	$142.60	11.130%	$158.4714	$158.47	$158.45	$158.50
7 purchase totals =	$717.72		$796.8046	$796.79	$796.85	$796.80