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	$82.37	12.405%	$92.588	$92.59	$92.60	$92.60
Purchase #2	$19.85	6.693%	$21.1786	$21.18	$21.20	$21.20
Purchase #3	$190.78	13.730%	$216.9741	$216.97	$216.95	$217.00
Purchase #4	$182.80	3.728%	$189.6148	$189.61	$189.60	$189.60
Purchase #5	$52.53	12.611%	$59.1546	$59.15	$59.15	$59.20
Purchase #6	$14.84	5.187%	$15.6098	$15.61	$15.60	$15.60
Purchase #7	$82.54	10.698%	$91.3701	$91.37	$91.35	$91.40
7 purchase totals =	$625.71		$686.4900	$686.48	$686.45	$686.60