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 $126.65   5.780%   $133.9704   $133.97   $133.95   $134.00  
  Purchase #2 $214.51   5.455%   $226.2115   $226.21   $226.20   $226.20  
  Purchase #3 $155.59   13.228%   $176.1714   $176.17   $176.15   $176.20  
  Purchase #4 $109.36   3.611%   $113.309   $113.31   $113.30   $113.30  
  Purchase #5 $210.38   4.189%   $219.1928   $219.19   $219.20   $219.20  
  Purchase #6 $70.55   11.291%   $78.5158   $78.52   $78.50   $78.50  
  Purchase #7 $229.37   13.284%   $259.8395   $259.84   $259.85   $259.80  
  7 purchase totals = $1,116.41       $1,207.2104   $1,207.21   $1,207.15   $1,207.20