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	$56.61	12.171%	$63.5	$63.50	$63.50	$63.50
Purchase #2	$51.78	5.171%	$54.4575	$54.46	$54.45	$54.50
Purchase #3	$39.52	12.178%	$44.3327	$44.33	$44.35	$44.30
Purchase #4	$180.95	10.181%	$199.3725	$199.37	$199.35	$199.40
Purchase #5	$39.63	13.377%	$44.9313	$44.93	$44.95	$44.90
Purchase #6	$30.98	13.866%	$35.2757	$35.28	$35.30	$35.30
Purchase #7	$198.95	12.335%	$223.4905	$223.49	$223.50	$223.50
7 purchase totals =	$598.42		$665.3602	$665.36	$665.40	$665.40