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 $43.29   7.862%   $46.6935   $46.69   $46.70   $46.70  
  Purchase #2 $171.68   6.481%   $182.8066   $182.81   $182.80   $182.80  
  Purchase #3 $244.91   9.313%   $267.7185   $267.72   $267.70   $267.70  
  Purchase #4 $125.54   7.106%   $134.4609   $134.46   $134.45   $134.50  
  Purchase #5 $104.76   7.736%   $112.8642   $112.86   $112.85   $112.90  
  Purchase #6 $217.63   6.264%   $231.2623   $231.26   $231.25   $231.30  
  Purchase #7 $33.48   5.862%   $35.4426   $35.44   $35.45   $35.40  
  7 purchase totals = $941.29       $1,011.2486   $1,011.24   $1,011.20   $1,011.30