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 $51.73   11.526%   $57.6924   $57.69   $57.70   $57.70  
  Purchase #2 $234.38   5.526%   $247.3318   $247.33   $247.35   $247.30  
  Purchase #3 $64.71   5.595%   $68.3305   $68.33   $68.35   $68.30  
  Purchase #4 $163.95   12.564%   $184.5487   $184.55   $184.55   $184.50  
  Purchase #5 $180.26   9.258%   $196.9485   $196.95   $196.95   $196.90  
  Purchase #6 $191.88   4.609%   $200.7237   $200.72   $200.70   $200.70  
  Purchase #7 $227.36   6.242%   $241.5518   $241.55   $241.55   $241.60  
  7 purchase totals = $1,114.27       $1,197.1274   $1,197.12   $1,197.15   $1,197.00