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 $196.86   4.585%   $205.886   $205.89   $205.90   $205.90  
  Purchase #2 $246.37   8.492%   $267.2917   $267.29   $267.30   $267.30  
  Purchase #3 $246.83   5.421%   $260.2107   $260.21   $260.20   $260.20  
  Purchase #4 $55.44   10.674%   $61.3577   $61.36   $61.35   $61.40  
  Purchase #5 $206.37   4.633%   $215.9311   $215.93   $215.95   $215.90  
  Purchase #6 $67.38   10.770%   $74.6368   $74.64   $74.65   $74.60  
  Purchase #7 $231.76   6.438%   $246.6807   $246.68   $246.70   $246.70  
  7 purchase totals = $1,251.01       $1,331.9947   $1,332.00   $1,332.05   $1,332.00