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 $208.26   8.850%   $226.691   $226.69   $226.70   $226.70  
  Purchase #2 $80.65   8.862%   $87.7972   $87.80   $87.80   $87.80  
  Purchase #3 $242.67   7.325%   $260.4456   $260.45   $260.45   $260.40  
  Purchase #4 $213.33   7.483%   $229.2935   $229.29   $229.30   $229.30  
  Purchase #5 $51.67   5.537%   $54.531   $54.53   $54.55   $54.50  
  Purchase #6 $46.58   5.521%   $49.1517   $49.15   $49.15   $49.20  
  Purchase #7 $102.53   13.764%   $116.6422   $116.64   $116.65   $116.60  
  7 purchase totals = $945.69       $1,024.5522   $1,024.55   $1,024.60   $1,024.50