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 $88.37   5.874%   $93.5609   $93.56   $93.55   $93.60  
  Purchase #2 $177.56   5.502%   $187.3294   $187.33   $187.35   $187.30  
  Purchase #3 $31.35   6.628%   $33.4279   $33.43   $33.45   $33.40  
  Purchase #4 $39.49   11.208%   $43.916   $43.92   $43.90   $43.90  
  Purchase #5 $69.81   5.837%   $73.8848   $73.88   $73.90   $73.90  
  Purchase #6 $46.30   10.662%   $51.2365   $51.24   $51.25   $51.20  
  Purchase #7 $200.91   9.455%   $219.906   $219.91   $219.90   $219.90  
  7 purchase totals = $653.79       $703.2615   $703.27   $703.30   $703.20