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	$98.83	12.327%	$111.0128	$111.01	$111.00	$111.00
Purchase #2	$120.54	4.655%	$126.1511	$126.15	$126.15	$126.20
Purchase #3	$79.78	4.435%	$83.3182	$83.32	$83.30	$83.30
Purchase #4	$117.33	6.561%	$125.028	$125.03	$125.05	$125.00
Purchase #5	$184.81	11.246%	$205.5937	$205.59	$205.60	$205.60
Purchase #6	$20.71	5.732%	$21.8971	$21.90	$21.90	$21.90
Purchase #7	$220.66	4.501%	$230.5919	$230.59	$230.60	$230.60
7 purchase totals =	$842.66		$903.5928	$903.59	$903.60	$903.60