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	$119.47	4.805%	$125.2105	$125.21	$125.20	$125.20
Purchase #2	$58.28	13.271%	$66.0143	$66.01	$66.00	$66.00
Purchase #3	$78.97	12.861%	$89.1263	$89.13	$89.15	$89.10
Purchase #4	$181.55	13.212%	$205.5364	$205.54	$205.55	$205.50
Purchase #5	$198.56	13.579%	$225.5225	$225.52	$225.50	$225.50
Purchase #6	$7.58	12.430%	$8.5222	$8.52	$8.50	$8.50
Purchase #7	$242.96	13.421%	$275.5677	$275.57	$275.55	$275.60
7 purchase totals =	$887.37		$995.4999	$995.50	$995.45	$995.40