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	$106.25	12.296%	$119.3145	$119.31	$119.30	$119.30
Purchase #2	$88.56	9.483%	$96.9581	$96.96	$96.95	$97.00
Purchase #3	$127.94	7.562%	$137.6148	$137.61	$137.60	$137.60
Purchase #4	$94.45	5.662%	$99.7978	$99.80	$99.80	$99.80
Purchase #5	$139.28	8.423%	$151.0116	$151.01	$151.00	$151.00
Purchase #6	$230.97	9.310%	$252.4733	$252.47	$252.45	$252.50
Purchase #7	$39.58	9.107%	$43.1846	$43.18	$43.20	$43.20
7 purchase totals =	$827.03		$900.3547	$900.34	$900.30	$900.40