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	$132.89	8.411%	$144.0674	$144.07	$144.05	$144.10
Purchase #2	$83.57	7.285%	$89.6581	$89.66	$89.65	$89.70
Purchase #3	$218.63	6.844%	$233.593	$233.59	$233.60	$233.60
Purchase #4	$12.50	4.187%	$13.0234	$13.02	$13.00	$13.00
Purchase #5	$12.75	13.319%	$14.4482	$14.45	$14.45	$14.40
Purchase #6	$201.92	8.574%	$219.2326	$219.23	$219.25	$219.20
Purchase #7	$250.67	12.304%	$281.5124	$281.51	$281.50	$281.50
7 purchase totals =	$912.93		$995.5351	$995.53	$995.50	$995.50