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 $88.49   8.785%   $96.2638   $96.26   $96.25   $96.30  
  Purchase #2 $213.90   10.226%   $235.7734   $235.77   $235.75   $235.80  
  Purchase #3 $223.71   4.697%   $234.2177   $234.22   $234.20   $234.20  
  Purchase #4 $154.74   10.625%   $171.1811   $171.18   $171.20   $171.20  
  Purchase #5 $199.47   4.474%   $208.3943   $208.39   $208.40   $208.40  
  Purchase #6 $82.74   3.569%   $85.693   $85.69   $85.70   $85.70  
  Purchase #7 $194.31   5.556%   $205.1059   $205.11   $205.10   $205.10  
  7 purchase totals = $1,157.36       $1,236.6292   $1,236.62   $1,236.60   $1,236.70