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 $182.33   6.432%   $194.0575   $194.06   $194.05   $194.10  
  Purchase #2 $190.99   8.254%   $206.7543   $206.75   $206.75   $206.80  
  Purchase #3 $184.51   5.312%   $194.3112   $194.31   $194.30   $194.30  
  Purchase #4 $241.28   10.685%   $267.0608   $267.06   $267.05   $267.10  
  Purchase #5 $106.70   10.484%   $117.8864   $117.89   $117.90   $117.90  
  Purchase #6 $232.92   6.420%   $247.8735   $247.87   $247.85   $247.90  
  Purchase #7 $121.84   12.234%   $136.7459   $136.75   $136.75   $136.70  
  7 purchase totals = $1,260.57       $1,364.6896   $1,364.69   $1,364.65   $1,364.80