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 $61.25   12.434%   $68.8658   $68.87   $68.85   $68.90  
  Purchase #2 $160.56   5.263%   $169.0103   $169.01   $169.00   $169.00  
  Purchase #3 $8.95   8.778%   $9.7356   $9.74   $9.75   $9.70  
  Purchase #4 $113.60   4.494%   $118.7052   $118.71   $118.70   $118.70  
  Purchase #5 $53.95   6.234%   $57.3132   $57.31   $57.30   $57.30  
  Purchase #6 $167.47   12.639%   $188.6365   $188.64   $188.65   $188.60  
  Purchase #7 $169.85   7.194%   $182.069   $182.07   $182.05   $182.10  
  7 purchase totals = $735.63       $794.3356   $794.35   $794.30   $794.30