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	$73.63	13.359%	$83.4662	$83.47	$83.45	$83.50
Purchase #2	$12.96	12.505%	$14.5806	$14.58	$14.60	$14.60
Purchase #3	$83.79	6.243%	$89.021	$89.02	$89.00	$89.00
Purchase #4	$175.43	3.316%	$181.2473	$181.25	$181.25	$181.20
Purchase #5	$203.32	9.626%	$222.8916	$222.89	$222.90	$222.90
Purchase #6	$200.34	10.756%	$221.8886	$221.89	$221.90	$221.90
Purchase #7	$150.86	12.538%	$169.7748	$169.77	$169.75	$169.80
7 purchase totals =	$900.33		$982.8701	$982.87	$982.85	$982.90