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	$182.32	9.173%	$199.0442	$199.04	$199.05	$199.00
Purchase #2	$179.57	8.833%	$195.4314	$195.43	$195.45	$195.40
Purchase #3	$95.45	13.277%	$108.1229	$108.12	$108.10	$108.10
Purchase #4	$124.49	5.421%	$131.2386	$131.24	$131.25	$131.20
Purchase #5	$93.73	12.492%	$105.4388	$105.44	$105.45	$105.40
Purchase #6	$126.48	10.280%	$139.4821	$139.48	$139.50	$139.50
Purchase #7	$180.37	11.151%	$200.4831	$200.48	$200.50	$200.50
7 purchase totals =	$982.41		$1,079.2411	$1,079.23	$1,079.30	$1,079.10