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 $89.48   13.552%   $101.6063   $101.61   $101.60   $101.60  
  Purchase #2 $181.70   9.614%   $199.1686   $199.17   $199.15   $199.20  
  Purchase #3 $95.27   3.742%   $98.835   $98.84   $98.85   $98.80  
  Purchase #4 $66.57   6.163%   $70.6727   $70.67   $70.65   $70.70  
  Purchase #5 $10.57   11.474%   $11.7828   $11.78   $11.80   $11.80  
  Purchase #6 $66.58   4.326%   $69.4603   $69.46   $69.45   $69.50  
  Purchase #7 $182.40   12.265%   $204.7714   $204.77   $204.75   $204.80  
  7 purchase totals = $692.57       $756.2971   $756.30   $756.25   $756.40