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 $73.83   3.315%   $76.2775   $76.28   $76.30   $76.30  
  Purchase #2 $233.75   3.393%   $241.6811   $241.68   $241.70   $241.70  
  Purchase #3 $54.25   12.512%   $61.0378   $61.04   $61.05   $61.00  
  Purchase #4 $207.62   12.859%   $234.3179   $234.32   $234.30   $234.30  
  Purchase #5 $87.71   7.364%   $94.169   $94.17   $94.15   $94.20  
  Purchase #6 $195.76   12.750%   $220.7194   $220.72   $220.70   $220.70  
  Purchase #7 $183.80   11.368%   $204.6944   $204.69   $204.70   $204.70  
  7 purchase totals = $1,036.72       $1,132.8971   $1,132.90   $1,132.90   $1,132.90