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 $85.38   10.116%   $94.017   $94.02   $94.00   $94.00  
  Purchase #2 $97.47   8.813%   $106.06   $106.06   $106.05   $106.10  
  Purchase #3 $246.64   4.510%   $257.7635   $257.76   $257.75   $257.80  
  Purchase #4 $161.90   10.588%   $179.042   $179.04   $179.05   $179.00  
  Purchase #5 $236.67   4.479%   $247.2704   $247.27   $247.25   $247.30  
  Purchase #6 $228.35   13.780%   $259.8166   $259.82   $259.80   $259.80  
  Purchase #7 $192.92   13.249%   $218.48   $218.48   $218.50   $218.50  
  7 purchase totals = $1,249.33       $1,362.4495   $1,362.45   $1,362.40   $1,362.50