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	$132.94	11.584%	$148.3398	$148.34	$148.35	$148.30
Purchase #2	$100.89	12.483%	$113.4841	$113.48	$113.50	$113.50
Purchase #3	$123.25	6.633%	$131.4252	$131.43	$131.45	$131.40
Purchase #4	$40.59	5.324%	$42.751	$42.75	$42.75	$42.80
Purchase #5	$163.78	3.829%	$170.0511	$170.05	$170.05	$170.10
Purchase #6	$16.83	4.786%	$17.6355	$17.64	$17.65	$17.60
Purchase #7	$68.86	8.563%	$74.7565	$74.76	$74.75	$74.80
7 purchase totals =	$647.14		$698.4432	$698.45	$698.50	$698.50