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 $67.67   7.306%   $72.614   $72.61   $72.60   $72.60  
  Purchase #2 $103.94   11.173%   $115.5532   $115.55   $115.55   $115.60  
  Purchase #3 $244.57   12.738%   $275.7233   $275.72   $275.70   $275.70  
  Purchase #4 $151.53   11.446%   $168.8741   $168.87   $168.85   $168.90  
  Purchase #5 $69.67   7.323%   $74.7719   $74.77   $74.75   $74.80  
  Purchase #6 $48.66   4.254%   $50.73   $50.73   $50.75   $50.70  
  Purchase #7 $238.39   11.500%   $265.8049   $265.80   $265.80   $265.80  
  7 purchase totals = $924.43       $1,024.0714   $1,024.05   $1,024.00   $1,024.10