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	$67.75	4.818%	$71.0142	$71.01	$71.00	$71.00
Purchase #2	$138.78	12.836%	$156.5938	$156.59	$156.60	$156.60
Purchase #3	$223.39	6.810%	$238.6029	$238.60	$238.60	$238.60
Purchase #4	$250.67	12.745%	$282.6179	$282.62	$282.60	$282.60
Purchase #5	$107.49	7.828%	$115.9043	$115.90	$115.90	$115.90
Purchase #6	$115.78	5.765%	$122.4547	$122.45	$122.45	$122.50
Purchase #7	$15.48	7.293%	$16.609	$16.61	$16.60	$16.60
7 purchase totals =	$919.34		$1,003.7968	$1,003.78	$1,003.75	$1,003.80