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	$107.37	5.141%	$112.8899	$112.89	$112.90	$112.90
Purchase #2	$82.81	4.371%	$86.4296	$86.43	$86.45	$86.40
Purchase #3	$248.50	10.523%	$274.6497	$274.65	$274.65	$274.60
Purchase #4	$164.47	4.618%	$172.0652	$172.07	$172.05	$172.10
Purchase #5	$141.38	3.433%	$146.2336	$146.23	$146.25	$146.20
Purchase #6	$155.32	4.158%	$161.7782	$161.78	$161.80	$161.80
Purchase #7	$130.37	8.334%	$141.235	$141.24	$141.25	$141.20
7 purchase totals =	$1,030.22		$1,095.2812	$1,095.29	$1,095.35	$1,095.20