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	$101.95	13.789%	$116.0079	$116.01	$116.00	$116.00
Purchase #2	$39.27	10.145%	$43.2539	$43.25	$43.25	$43.30
Purchase #3	$129.60	11.730%	$144.8021	$144.80	$144.80	$144.80
Purchase #4	$6.29	11.322%	$7.0022	$7.00	$7.00	$7.00
Purchase #5	$147.65	7.239%	$158.3384	$158.34	$158.35	$158.30
Purchase #6	$100.81	12.103%	$113.011	$113.01	$113.00	$113.00
Purchase #7	$86.38	10.558%	$95.5	$95.50	$95.50	$95.50
7 purchase totals =	$611.95		$677.9155	$677.91	$677.90	$677.90