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 $213.66   10.574%   $236.2524   $236.25   $236.25   $236.30  
  Purchase #2 $211.30   4.320%   $220.4282   $220.43   $220.45   $220.40  
  Purchase #3 $107.67   10.287%   $118.746   $118.75   $118.75   $118.70  
  Purchase #4 $230.54   11.777%   $257.6907   $257.69   $257.70   $257.70  
  Purchase #5 $22.54   10.323%   $24.8668   $24.87   $24.85   $24.90  
  Purchase #6 $45.80   10.500%   $50.609   $50.61   $50.60   $50.60  
  Purchase #7 $133.63   8.857%   $145.4656   $145.47   $145.45   $145.50  
  7 purchase totals = $965.14       $1,054.0587   $1,054.07   $1,054.05   $1,054.10