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	$170.93	5.743%	$180.7465	$180.75	$180.75	$180.70
Purchase #2	$139.25	10.757%	$154.2291	$154.23	$154.25	$154.20
Purchase #3	$248.98	6.611%	$265.4401	$265.44	$265.45	$265.40
Purchase #4	$63.59	13.786%	$72.3565	$72.36	$72.35	$72.40
Purchase #5	$102.82	8.518%	$111.5782	$111.58	$111.60	$111.60
Purchase #6	$95.53	5.196%	$100.4937	$100.49	$100.50	$100.50
Purchase #7	$177.77	11.441%	$198.1087	$198.11	$198.10	$198.10
7 purchase totals =	$998.87		$1,082.9528	$1,082.96	$1,083.00	$1,082.90