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	$140.47	4.260%	$146.454	$146.45	$146.45	$146.50
Purchase #2	$86.78	5.433%	$91.4948	$91.49	$91.50	$91.50
Purchase #3	$141.86	3.276%	$146.5073	$146.51	$146.50	$146.50
Purchase #4	$10.49	4.346%	$10.9459	$10.95	$10.95	$10.90
Purchase #5	$152.59	10.660%	$168.8561	$168.86	$168.85	$168.90
Purchase #6	$110.96	12.774%	$125.134	$125.13	$125.15	$125.10
Purchase #7	$179.57	12.730%	$202.4293	$202.43	$202.45	$202.40
7 purchase totals =	$822.72		$891.8214	$891.82	$891.85	$891.80