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 $69.26   9.333%   $75.724   $75.72   $75.70   $75.70  
  Purchase #2 $67.25   11.783%   $75.1741   $75.17   $75.15   $75.20  
  Purchase #3 $192.71   6.313%   $204.8758   $204.88   $204.90   $204.90  
  Purchase #4 $220.26   3.169%   $227.24   $227.24   $227.25   $227.20  
  Purchase #5 $213.67   3.348%   $220.8237   $220.82   $220.80   $220.80  
  Purchase #6 $12.35   12.794%   $13.9301   $13.93   $13.95   $13.90  
  Purchase #7 $199.46   3.693%   $206.8261   $206.83   $206.85   $206.80  
  7 purchase totals = $974.96       $1,024.5938   $1,024.59   $1,024.60   $1,024.50