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 $216.36   9.186%   $236.2348   $236.23   $236.25   $236.20  
  Purchase #2 $68.66   10.325%   $75.7491   $75.75   $75.75   $75.70  
  Purchase #3 $113.74   11.869%   $127.2398   $127.24   $127.25   $127.20  
  Purchase #4 $92.37   4.171%   $96.2228   $96.22   $96.20   $96.20  
  Purchase #5 $210.57   5.584%   $222.3282   $222.33   $222.35   $222.30  
  Purchase #6 $199.87   6.713%   $213.2873   $213.29   $213.30   $213.30  
  Purchase #7 $152.36   7.449%   $163.7093   $163.71   $163.70   $163.70  
  7 purchase totals = $1,053.93       $1,134.7713   $1,134.77   $1,134.80   $1,134.60