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	$106.25	12.229%	$119.2433	$119.24	$119.25	$119.20
Purchase #2	$130.42	9.279%	$142.5217	$142.52	$142.50	$142.50
Purchase #3	$143.82	5.714%	$152.0379	$152.04	$152.05	$152.00
Purchase #4	$92.52	5.516%	$97.6234	$97.62	$97.60	$97.60
Purchase #5	$129.37	7.776%	$139.4298	$139.43	$139.45	$139.40
Purchase #6	$206.67	5.757%	$218.568	$218.57	$218.55	$218.60
Purchase #7	$221.56	3.625%	$229.5916	$229.59	$229.60	$229.60
7 purchase totals =	$1,030.61		$1,099.0157	$1,099.01	$1,099.00	$1,098.90