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	$224.41	9.607%	$245.9691	$245.97	$245.95	$246.00
Purchase #2	$233.84	9.213%	$255.3837	$255.38	$255.40	$255.40
Purchase #3	$242.74	13.795%	$276.226	$276.23	$276.25	$276.20
Purchase #4	$81.86	13.503%	$92.9136	$92.91	$92.90	$92.90
Purchase #5	$93.35	7.555%	$100.4026	$100.40	$100.40	$100.40
Purchase #6	$136.57	7.496%	$146.8073	$146.81	$146.80	$146.80
Purchase #7	$87.94	13.561%	$99.8655	$99.87	$99.85	$99.90
7 purchase totals =	$1,100.71		$1,217.5678	$1,217.57	$1,217.55	$1,217.60