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 $56.64   7.271%   $60.7583   $60.76   $60.75   $60.80  
  Purchase #2 $233.60   4.445%   $243.9835   $243.98   $244.00   $244.00  
  Purchase #3 $13.48   11.157%   $14.984   $14.98   $15.00   $15.00  
  Purchase #4 $250.30   5.492%   $264.0465   $264.05   $264.05   $264.00  
  Purchase #5 $197.59   8.669%   $214.7191   $214.72   $214.70   $214.70  
  Purchase #6 $242.73   11.212%   $269.9449   $269.94   $269.95   $269.90  
  Purchase #7 $62.63   7.168%   $67.1193   $67.12   $67.10   $67.10  
  7 purchase totals = $1,056.97       $1,135.5556   $1,135.55   $1,135.55   $1,135.50