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 $176.39   9.785%   $193.6498   $193.65   $193.65   $193.60  
  Purchase #2 $95.95   10.421%   $105.9489   $105.95   $105.95   $105.90  
  Purchase #3 $41.34   11.122%   $45.9378   $45.94   $45.95   $45.90  
  Purchase #4 $32.58   12.228%   $36.5639   $36.56   $36.55   $36.60  
  Purchase #5 $232.48   11.103%   $258.2923   $258.29   $258.30   $258.30  
  Purchase #6 $212.70   12.782%   $239.8873   $239.89   $239.90   $239.90  
  Purchase #7 $190.53   7.484%   $204.7893   $204.79   $204.80   $204.80  
  7 purchase totals = $981.97       $1,085.0693   $1,085.07   $1,085.10   $1,085.00