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 $62.90   9.574%   $68.922   $68.92   $68.90   $68.90  
  Purchase #2 $183.28   11.600%   $204.5405   $204.54   $204.55   $204.50  
  Purchase #3 $241.41   6.277%   $256.5633   $256.56   $256.55   $256.60  
  Purchase #4 $217.88   9.487%   $238.5503   $238.55   $238.55   $238.60  
  Purchase #5 $154.38   5.701%   $163.1812   $163.18   $163.20   $163.20  
  Purchase #6 $248.74   3.700%   $257.9434   $257.94   $257.95   $257.90  
  Purchase #7 $52.76   12.226%   $59.2104   $59.21   $59.20   $59.20  
  7 purchase totals = $1,161.35       $1,248.9111   $1,248.90   $1,248.90   $1,248.90