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	$116.93	12.829%	$131.9309	$131.93	$131.95	$131.90
Purchase #2	$72.71	4.871%	$76.2517	$76.25	$76.25	$76.30
Purchase #3	$163.29	4.489%	$170.6201	$170.62	$170.60	$170.60
Purchase #4	$202.27	9.285%	$221.0508	$221.05	$221.05	$221.10
Purchase #5	$154.37	6.789%	$164.8502	$164.85	$164.85	$164.90
Purchase #6	$237.46	3.397%	$245.5265	$245.53	$245.55	$245.50
Purchase #7	$50.78	9.741%	$55.7265	$55.73	$55.75	$55.70
7 purchase totals =	$997.81		$1,065.9567	$1,065.96	$1,066.00	$1,066.00