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 $65.78   4.330%   $68.6283   $68.63   $68.65   $68.60  
  Purchase #2 $240.84   6.833%   $257.2966   $257.30   $257.30   $257.30  
  Purchase #3 $12.66   12.336%   $14.2217   $14.22   $14.20   $14.20  
  Purchase #4 $165.85   3.274%   $171.2799   $171.28   $171.30   $171.30  
  Purchase #5 $44.94   7.751%   $48.4233   $48.42   $48.40   $48.40  
  Purchase #6 $179.58   13.338%   $203.5324   $203.53   $203.55   $203.50  
  Purchase #7 $172.59   11.400%   $192.2653   $192.27   $192.25   $192.30  
  7 purchase totals = $882.24       $955.6475   $955.65   $955.65   $955.60