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	$102.57	9.426%	$112.2382	$112.24	$112.25	$112.20
Purchase #2	$222.37	3.670%	$230.531	$230.53	$230.55	$230.50
Purchase #3	$133.76	6.838%	$142.9065	$142.91	$142.90	$142.90
Purchase #4	$99.99	3.721%	$103.7106	$103.71	$103.70	$103.70
Purchase #5	$81.34	11.690%	$90.8486	$90.85	$90.85	$90.80
Purchase #6	$70.29	8.310%	$76.1311	$76.13	$76.15	$76.10
Purchase #7	$151.31	3.148%	$156.0732	$156.07	$156.05	$156.10
7 purchase totals =	$861.63		$912.4392	$912.44	$912.45	$912.30