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 $127.81   4.729%   $133.8541   $133.85   $133.85   $133.90  
  Purchase #2 $32.53   6.456%   $34.6301   $34.63   $34.65   $34.60  
  Purchase #3 $64.30   7.647%   $69.217   $69.22   $69.20   $69.20  
  Purchase #4 $105.41   7.657%   $113.4812   $113.48   $113.50   $113.50  
  Purchase #5 $58.89   6.457%   $62.6925   $62.69   $62.70   $62.70  
  Purchase #6 $247.72   3.135%   $255.486   $255.49   $255.50   $255.50  
  Purchase #7 $248.29   9.730%   $272.4486   $272.45   $272.45   $272.40  
  7 purchase totals = $884.95       $941.8095   $941.81   $941.85   $941.80