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 $152.25   10.846%   $168.763   $168.76   $168.75   $168.80  
  Purchase #2 $61.43   12.314%   $68.9945   $68.99   $69.00   $69.00  
  Purchase #3 $167.64   7.306%   $179.8878   $179.89   $179.90   $179.90  
  Purchase #4 $77.44   10.863%   $85.8523   $85.85   $85.85   $85.90  
  Purchase #5 $104.50   12.691%   $117.7621   $117.76   $117.75   $117.80  
  Purchase #6 $204.56   4.331%   $213.4195   $213.42   $213.40   $213.40  
  Purchase #7 $249.63   4.262%   $260.2692   $260.27   $260.25   $260.30  
  7 purchase totals = $1,017.45       $1,094.9484   $1,094.94   $1,094.90   $1,095.10