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	$116.78	5.845%	$123.6058	$123.61	$123.60	$123.60
Purchase #2	$179.33	10.667%	$198.4591	$198.46	$198.45	$198.50
Purchase #3	$78.49	9.567%	$85.9991	$86.00	$86.00	$86.00
Purchase #4	$94.28	4.108%	$98.153	$98.15	$98.15	$98.20
Purchase #5	$97.38	4.220%	$101.4894	$101.49	$101.50	$101.50
Purchase #6	$215.83	10.213%	$237.8727	$237.87	$237.85	$237.90
Purchase #7	$155.83	5.553%	$164.4832	$164.48	$164.50	$164.50
7 purchase totals =	$937.92		$1,010.0623	$1,010.06	$1,010.05	$1,010.20