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	$119.89	6.695%	$127.9166	$127.92	$127.90	$127.90
Purchase #2	$66.96	7.325%	$71.8648	$71.86	$71.85	$71.90
Purchase #3	$5.77	12.305%	$6.48	$6.48	$6.50	$6.50
Purchase #4	$227.97	12.171%	$255.7162	$255.72	$255.70	$255.70
Purchase #5	$228.46	10.535%	$252.5283	$252.53	$252.55	$252.50
Purchase #6	$228.38	6.646%	$243.5581	$243.56	$243.55	$243.60
Purchase #7	$7.31	9.538%	$8.0072	$8.01	$8.00	$8.00
7 purchase totals =	$884.74		$966.0712	$966.08	$966.05	$966.10