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 $71.86   6.663%   $76.648   $76.65   $76.65   $76.60  
  Purchase #2 $118.29   13.272%   $133.9894   $133.99   $134.00   $134.00  
  Purchase #3 $174.82   5.694%   $184.7743   $184.77   $184.75   $184.80  
  Purchase #4 $162.97   4.249%   $169.8946   $169.89   $169.90   $169.90  
  Purchase #5 $165.47   6.776%   $176.6822   $176.68   $176.70   $176.70  
  Purchase #6 $243.86   5.801%   $258.0063   $258.01   $258.00   $258.00  
  Purchase #7 $238.56   4.307%   $248.8348   $248.83   $248.85   $248.80  
  7 purchase totals = $1,175.83       $1,248.8296   $1,248.82   $1,248.85   $1,248.80