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 $192.67   5.276%   $202.8353   $202.84   $202.85   $202.80  
  Purchase #2 $241.84   3.632%   $250.6236   $250.62   $250.60   $250.60  
  Purchase #3 $226.93   7.278%   $243.446   $243.45   $243.45   $243.40  
  Purchase #4 $88.74   6.529%   $94.5338   $94.53   $94.55   $94.50  
  Purchase #5 $235.49   12.784%   $265.595   $265.60   $265.60   $265.60  
  Purchase #6 $133.99   5.676%   $141.5953   $141.60   $141.60   $141.60  
  Purchase #7 $199.76   6.844%   $213.4316   $213.43   $213.45   $213.40  
  7 purchase totals = $1,319.42       $1,412.0606   $1,412.07   $1,412.10   $1,411.90