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	$56.25	5.576%	$59.3865	$59.39	$59.40	$59.40
Purchase #2	$74.53	8.149%	$80.6034	$80.60	$80.60	$80.60
Purchase #3	$104.84	8.652%	$113.9108	$113.91	$113.90	$113.90
Purchase #4	$116.40	6.208%	$123.6261	$123.63	$123.65	$123.60
Purchase #5	$177.30	4.460%	$185.2076	$185.21	$185.20	$185.20
Purchase #6	$61.38	9.497%	$67.2093	$67.21	$67.20	$67.20
Purchase #7	$126.88	3.213%	$130.9567	$130.96	$130.95	$131.00
7 purchase totals =	$717.58		$760.9004	$760.91	$760.90	$760.90