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 $58.86   8.212%   $63.6936   $63.69   $63.70   $63.70  
  Purchase #2 $181.33   11.653%   $202.4604   $202.46   $202.45   $202.50  
  Purchase #3 $142.92   10.622%   $158.101   $158.10   $158.10   $158.10  
  Purchase #4 $210.74   13.379%   $238.9349   $238.93   $238.95   $238.90  
  Purchase #5 $144.36   8.475%   $156.5945   $156.59   $156.60   $156.60  
  Purchase #6 $187.37   7.189%   $200.84   $200.84   $200.85   $200.80  
  Purchase #7 $151.29   8.131%   $163.5914   $163.59   $163.60   $163.60  
  7 purchase totals = $1,076.87       $1,184.2158   $1,184.20   $1,184.25   $1,184.20