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	$135.27	7.826%	$145.8562	$145.86	$145.85	$145.90
Purchase #2	$199.38	10.866%	$221.0446	$221.04	$221.05	$221.00
Purchase #3	$33.85	12.286%	$38.0088	$38.01	$38.00	$38.00
Purchase #4	$125.46	10.614%	$138.7763	$138.78	$138.80	$138.80
Purchase #5	$134.93	12.125%	$151.2903	$151.29	$151.30	$151.30
Purchase #6	$44.89	5.846%	$47.5143	$47.51	$47.50	$47.50
Purchase #7	$188.33	6.242%	$200.0856	$200.09	$200.10	$200.10
7 purchase totals =	$862.11		$942.5761	$942.58	$942.60	$942.60