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 $151.49   9.514%   $165.9028   $165.90   $165.90   $165.90  
  Purchase #2 $23.71   13.527%   $26.9173   $26.92   $26.90   $26.90  
  Purchase #3 $84.91   8.547%   $92.1673   $92.17   $92.15   $92.20  
  Purchase #4 $105.79   3.402%   $109.389   $109.39   $109.40   $109.40  
  Purchase #5 $219.64   12.437%   $246.9566   $246.96   $246.95   $247.00  
  Purchase #6 $26.38   5.578%   $27.8515   $27.85   $27.85   $27.90  
  Purchase #7 $39.60   12.781%   $44.6613   $44.66   $44.65   $44.70  
  7 purchase totals = $651.52       $713.8458   $713.85   $713.80   $714.00