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 $33.95   5.329%   $35.7592   $35.76   $35.75   $35.80  
  Purchase #2 $112.27   5.773%   $118.7513   $118.75   $118.75   $118.80  
  Purchase #3 $88.77   5.152%   $93.3434   $93.34   $93.35   $93.30  
  Purchase #4 $170.27   5.219%   $179.1564   $179.16   $179.15   $179.20  
  Purchase #5 $7.56   9.829%   $8.3031   $8.30   $8.30   $8.30  
  Purchase #6 $139.39   7.754%   $150.1983   $150.20   $150.20   $150.20  
  Purchase #7 $219.62   13.221%   $248.656   $248.66   $248.65   $248.70  
  7 purchase totals = $771.83       $834.1677   $834.17   $834.15   $834.30