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	$18.66	3.854%	$19.3792	$19.38	$19.40	$19.40
Purchase #2	$151.32	12.788%	$170.6708	$170.67	$170.65	$170.70
Purchase #3	$145.56	3.555%	$150.7347	$150.73	$150.75	$150.70
Purchase #4	$33.85	10.344%	$37.3514	$37.35	$37.35	$37.40
Purchase #5	$59.69	6.607%	$63.6337	$63.63	$63.65	$63.60
Purchase #6	$48.35	5.645%	$51.0794	$51.08	$51.10	$51.10
Purchase #7	$66.34	9.509%	$72.6483	$72.65	$72.65	$72.60
7 purchase totals =	$523.77		$565.4975	$565.49	$565.55	$565.50