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	$67.57	5.776%	$71.4728	$71.47	$71.45	$71.50
Purchase #2	$79.48	3.846%	$82.5368	$82.54	$82.55	$82.50
Purchase #3	$179.29	6.348%	$190.6713	$190.67	$190.65	$190.70
Purchase #4	$160.66	13.438%	$182.2495	$182.25	$182.25	$182.20
Purchase #5	$238.55	11.522%	$266.0357	$266.04	$266.05	$266.00
Purchase #6	$229.81	13.153%	$260.0369	$260.04	$260.05	$260.00
Purchase #7	$11.65	6.214%	$12.3739	$12.37	$12.35	$12.40
7 purchase totals =	$967.01		$1,065.3769	$1,065.38	$1,065.35	$1,065.30