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 $95.66   7.264%   $102.6087   $102.61   $102.60   $102.60  
  Purchase #2 $231.47   10.667%   $256.1609   $256.16   $256.15   $256.20  
  Purchase #3 $125.96   7.423%   $135.31   $135.31   $135.30   $135.30  
  Purchase #4 $89.38   7.837%   $96.3847   $96.38   $96.40   $96.40  
  Purchase #5 $77.34   6.488%   $82.3578   $82.36   $82.35   $82.40  
  Purchase #6 $157.60   4.432%   $164.5848   $164.58   $164.60   $164.60  
  Purchase #7 $247.26   11.752%   $276.318   $276.32   $276.30   $276.30  
  7 purchase totals = $1,024.67       $1,113.7249   $1,113.72   $1,113.70   $1,113.80