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 $188.75   7.416%   $202.7477   $202.75   $202.75   $202.70  
  Purchase #2 $59.81   6.111%   $63.465   $63.47   $63.45   $63.50  
  Purchase #3 $173.37   11.274%   $192.9157   $192.92   $192.90   $192.90  
  Purchase #4 $143.34   8.623%   $155.7002   $155.70   $155.70   $155.70  
  Purchase #5 $154.53   7.191%   $165.6423   $165.64   $165.65   $165.60  
  Purchase #6 $87.54   12.118%   $98.1481   $98.15   $98.15   $98.10  
  Purchase #7 $59.64   7.228%   $63.9508   $63.95   $63.95   $64.00  
  7 purchase totals = $866.98       $942.5698   $942.58   $942.55   $942.50