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	$75.43	6.761%	$80.5298	$80.53	$80.55	$80.50
Purchase #2	$76.92	10.728%	$85.172	$85.17	$85.15	$85.20
Purchase #3	$14.26	11.310%	$15.8728	$15.87	$15.85	$15.90
Purchase #4	$150.42	11.789%	$168.153	$168.15	$168.15	$168.20
Purchase #5	$208.83	8.241%	$226.0397	$226.04	$226.05	$226.00
Purchase #6	$5.80	5.711%	$6.1312	$6.13	$6.15	$6.10
Purchase #7	$29.73	9.134%	$32.4455	$32.45	$32.45	$32.40
7 purchase totals =	$561.39		$614.3440	$614.34	$614.35	$614.30