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 $71.37   3.580%   $73.925   $73.93   $73.95   $73.90  
  Purchase #2 $153.39   8.177%   $165.9327   $165.93   $165.95   $165.90  
  Purchase #3 $56.61   7.299%   $60.742   $60.74   $60.75   $60.70  
  Purchase #4 $243.87   7.312%   $261.7018   $261.70   $261.70   $261.70  
  Purchase #5 $169.56   4.720%   $177.5632   $177.56   $177.55   $177.60  
  Purchase #6 $85.54   6.784%   $91.343   $91.34   $91.35   $91.30  
  Purchase #7 $228.38   4.210%   $237.9948   $237.99   $238.00   $238.00  
  7 purchase totals = $1,008.72       $1,069.2025   $1,069.19   $1,069.25   $1,069.10