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	$40.99	6.196%	$43.5297	$43.53	$43.55	$43.50
Purchase #2	$45.55	13.462%	$51.6819	$51.68	$51.70	$51.70
Purchase #3	$135.33	6.601%	$144.2631	$144.26	$144.25	$144.30
Purchase #4	$161.52	13.616%	$183.5126	$183.51	$183.50	$183.50
Purchase #5	$157.56	3.174%	$162.561	$162.56	$162.55	$162.60
Purchase #6	$164.40	4.706%	$172.1367	$172.14	$172.15	$172.10
Purchase #7	$236.37	3.180%	$243.8866	$243.89	$243.90	$243.90
7 purchase totals =	$941.72		$1,001.5716	$1,001.57	$1,001.60	$1,001.60