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 $207.68   6.536%   $221.254   $221.25   $221.25   $221.30  
  Purchase #2 $243.60   4.562%   $254.713   $254.71   $254.70   $254.70  
  Purchase #3 $145.77   12.650%   $164.2099   $164.21   $164.20   $164.20  
  Purchase #4 $243.50   9.131%   $265.734   $265.73   $265.75   $265.70  
  Purchase #5 $87.52   7.622%   $94.1908   $94.19   $94.20   $94.20  
  Purchase #6 $111.31   5.719%   $117.6758   $117.68   $117.70   $117.70  
  Purchase #7 $15.78   12.613%   $17.7703   $17.77   $17.75   $17.80  
  7 purchase totals = $1,055.16       $1,135.5478   $1,135.54   $1,135.55   $1,135.60