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	$36.28	3.167%	$37.429	$37.43	$37.45	$37.40
Purchase #2	$228.97	5.584%	$241.7557	$241.76	$241.75	$241.80
Purchase #3	$81.69	4.697%	$85.527	$85.53	$85.55	$85.50
Purchase #4	$61.26	8.352%	$66.3764	$66.38	$66.40	$66.40
Purchase #5	$117.29	8.595%	$127.3711	$127.37	$127.35	$127.40
Purchase #6	$169.85	9.324%	$185.6868	$185.69	$185.70	$185.70
Purchase #7	$20.53	13.206%	$23.2412	$23.24	$23.25	$23.20
7 purchase totals =	$715.87		$767.3872	$767.40	$767.45	$767.40