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	$100.63	10.817%	$111.5151	$111.52	$111.50	$111.50
Purchase #2	$48.46	3.197%	$50.0093	$50.01	$50.00	$50.00
Purchase #3	$80.47	12.183%	$90.2737	$90.27	$90.25	$90.30
Purchase #4	$110.86	13.225%	$125.5212	$125.52	$125.50	$125.50
Purchase #5	$150.50	3.538%	$155.8247	$155.82	$155.80	$155.80
Purchase #6	$181.32	10.626%	$200.5871	$200.59	$200.60	$200.60
Purchase #7	$91.65	8.490%	$99.4311	$99.43	$99.45	$99.40
7 purchase totals =	$763.89		$833.1622	$833.16	$833.10	$833.10