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 $68.73   3.184%   $70.9184   $70.92   $70.90   $70.90  
  Purchase #2 $198.91   3.836%   $206.5402   $206.54   $206.55   $206.50  
  Purchase #3 $198.89   5.872%   $210.5688   $210.57   $210.55   $210.60  
  Purchase #4 $112.29   4.298%   $117.1162   $117.12   $117.10   $117.10  
  Purchase #5 $155.54   11.864%   $173.9933   $173.99   $174.00   $174.00  
  Purchase #6 $237.45   12.696%   $267.5967   $267.60   $267.60   $267.60  
  Purchase #7 $136.68   8.476%   $148.265   $148.27   $148.25   $148.30  
  7 purchase totals = $1,108.49       $1,194.9986   $1,195.01   $1,194.95   $1,195.00