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 $87.79   8.162%   $94.9554   $94.96   $94.95   $95.00  
  Purchase #2 $92.31   5.556%   $97.4387   $97.44   $97.45   $97.40  
  Purchase #3 $81.36   5.165%   $85.5622   $85.56   $85.55   $85.60  
  Purchase #4 $113.90   3.588%   $117.9867   $117.99   $118.00   $118.00  
  Purchase #5 $166.93   10.743%   $184.8633   $184.86   $184.85   $184.90  
  Purchase #6 $102.29   11.830%   $114.3909   $114.39   $114.40   $114.40  
  Purchase #7 $213.73   5.501%   $225.4873   $225.49   $225.50   $225.50  
  7 purchase totals = $858.31       $920.6845   $920.69   $920.70   $920.80