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	$161.42	12.334%	$181.3295	$181.33	$181.35	$181.30
Purchase #2	$92.56	8.851%	$100.7525	$100.75	$100.75	$100.80
Purchase #3	$120.30	7.665%	$129.521	$129.52	$129.50	$129.50
Purchase #4	$34.75	3.496%	$35.9649	$35.96	$35.95	$36.00
Purchase #5	$19.62	13.856%	$22.3385	$22.34	$22.35	$22.30
Purchase #6	$152.72	10.566%	$168.8564	$168.86	$168.85	$168.90
Purchase #7	$98.31	13.496%	$111.5779	$111.58	$111.60	$111.60
7 purchase totals =	$679.68		$750.3407	$750.34	$750.35	$750.40