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	$202.52	10.686%	$224.1613	$224.16	$224.15	$224.20
Purchase #2	$34.47	4.292%	$35.9495	$35.95	$35.95	$35.90
Purchase #3	$82.88	9.398%	$90.6691	$90.67	$90.65	$90.70
Purchase #4	$47.75	9.643%	$52.3545	$52.35	$52.35	$52.40
Purchase #5	$234.84	8.693%	$255.2546	$255.25	$255.25	$255.30
Purchase #6	$194.85	9.388%	$213.1425	$213.14	$213.15	$213.10
Purchase #7	$89.29	7.284%	$95.7939	$95.79	$95.80	$95.80
7 purchase totals =	$886.60		$967.3254	$967.31	$967.30	$967.40