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 $30.41   8.551%   $33.0104   $33.01   $33.00   $33.00  
  Purchase #2 $242.59   8.803%   $263.9452   $263.95   $263.95   $263.90  
  Purchase #3 $227.89   8.348%   $246.9143   $246.91   $246.90   $246.90  
  Purchase #4 $191.94   8.254%   $207.7827   $207.78   $207.80   $207.80  
  Purchase #5 $47.28   8.552%   $51.3234   $51.32   $51.30   $51.30  
  Purchase #6 $98.97   4.472%   $103.3959   $103.40   $103.40   $103.40  
  Purchase #7 $222.98   10.857%   $247.1889   $247.19   $247.20   $247.20  
  7 purchase totals = $1,062.06       $1,153.5608   $1,153.56   $1,153.55   $1,153.50