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 $104.87   8.762%   $114.0587   $114.06   $114.05   $114.10  
  Purchase #2 $60.99   3.236%   $62.9636   $62.96   $62.95   $63.00  
  Purchase #3 $169.35   4.651%   $177.2265   $177.23   $177.25   $177.20  
  Purchase #4 $205.47   3.815%   $213.3087   $213.31   $213.30   $213.30  
  Purchase #5 $247.37   3.755%   $256.6587   $256.66   $256.65   $256.70  
  Purchase #6 $183.93   11.397%   $204.8925   $204.89   $204.90   $204.90  
  Purchase #7 $41.88   5.172%   $44.046   $44.05   $44.05   $44.00  
  7 purchase totals = $1,013.86       $1,073.1547   $1,073.16   $1,073.15   $1,073.20