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	$32.92	5.410%	$34.701	$34.70	$34.70	$34.70
Purchase #2	$101.48	3.827%	$105.3636	$105.36	$105.35	$105.40
Purchase #3	$63.97	3.830%	$66.4201	$66.42	$66.40	$66.40
Purchase #4	$117.43	8.532%	$127.4491	$127.45	$127.45	$127.40
Purchase #5	$208.86	3.673%	$216.5314	$216.53	$216.55	$216.50
Purchase #6	$127.46	11.777%	$142.471	$142.47	$142.45	$142.50
Purchase #7	$47.77	3.266%	$49.3302	$49.33	$49.35	$49.30
7 purchase totals =	$699.89		$742.2664	$742.26	$742.25	$742.20