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 $58.59   6.628%   $62.4733   $62.47   $62.45   $62.50  
  Purchase #2 $36.94   11.122%   $41.0485   $41.05   $41.05   $41.00  
  Purchase #3 $62.35   13.819%   $70.9661   $70.97   $70.95   $71.00  
  Purchase #4 $21.80   13.472%   $24.7369   $24.74   $24.75   $24.70  
  Purchase #5 $33.84   8.217%   $36.6206   $36.62   $36.60   $36.60  
  Purchase #6 $211.37   7.573%   $227.3771   $227.38   $227.40   $227.40  
  Purchase #7 $228.61   5.580%   $241.3664   $241.37   $241.35   $241.40  
  7 purchase totals = $653.50       $704.5889   $704.60   $704.55   $704.60