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	$63.53	4.411%	$66.3323	$66.33	$66.35	$66.30
Purchase #2	$97.26	4.363%	$101.5035	$101.50	$101.50	$101.50
Purchase #3	$82.81	8.505%	$89.853	$89.85	$89.85	$89.90
Purchase #4	$133.66	10.243%	$147.3508	$147.35	$147.35	$147.40
Purchase #5	$124.38	9.514%	$136.2135	$136.21	$136.20	$136.20
Purchase #6	$148.52	5.358%	$156.4777	$156.48	$156.50	$156.50
Purchase #7	$39.39	13.663%	$44.7719	$44.77	$44.75	$44.80
7 purchase totals =	$689.55		$742.5027	$742.49	$742.50	$742.60