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 $201.89   6.132%   $214.2699   $214.27   $214.25   $214.30  
  Purchase #2 $44.57   7.434%   $47.8833   $47.88   $47.90   $47.90  
  Purchase #3 $110.25   10.324%   $121.6322   $121.63   $121.65   $121.60  
  Purchase #4 $202.57   7.353%   $217.465   $217.47   $217.45   $217.50  
  Purchase #5 $163.42   6.404%   $173.8854   $173.89   $173.90   $173.90  
  Purchase #6 $113.66   7.246%   $121.8958   $121.90   $121.90   $121.90  
  Purchase #7 $120.86   6.104%   $128.2373   $128.24   $128.25   $128.20  
  7 purchase totals = $957.22       $1,025.2689   $1,025.28   $1,025.30   $1,025.30