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	$40.31	7.470%	$43.3212	$43.32	$43.30	$43.30
Purchase #2	$97.63	7.554%	$105.005	$105.01	$105.00	$105.00
Purchase #3	$116.77	8.172%	$126.3124	$126.31	$126.30	$126.30
Purchase #4	$77.38	3.464%	$80.0604	$80.06	$80.05	$80.10
Purchase #5	$18.33	11.149%	$20.3736	$20.37	$20.35	$20.40
Purchase #6	$140.95	4.260%	$146.9545	$146.95	$146.95	$147.00
Purchase #7	$45.73	3.249%	$47.2158	$47.22	$47.20	$47.20
7 purchase totals =	$537.10		$569.2429	$569.24	$569.15	$569.30