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 $183.98   6.478%   $195.8982   $195.90   $195.90   $195.90  
  Purchase #2 $217.94   7.459%   $234.1961   $234.20   $234.20   $234.20  
  Purchase #3 $59.38   6.290%   $63.115   $63.12   $63.10   $63.10  
  Purchase #4 $246.98   4.751%   $258.714   $258.71   $258.70   $258.70  
  Purchase #5 $100.39   7.304%   $107.7225   $107.72   $107.70   $107.70  
  Purchase #6 $15.89   5.358%   $16.7414   $16.74   $16.75   $16.70  
  Purchase #7 $55.35   7.180%   $59.3241   $59.32   $59.30   $59.30  
  7 purchase totals = $879.91       $935.7113   $935.71   $935.65   $935.60