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 $213.87   9.410%   $233.9952   $234.00   $234.00   $234.00  
  Purchase #2 $152.50   12.591%   $171.7013   $171.70   $171.70   $171.70  
  Purchase #3 $200.77   13.430%   $227.7334   $227.73   $227.75   $227.70  
  Purchase #4 $82.43   3.254%   $85.1123   $85.11   $85.10   $85.10  
  Purchase #5 $32.60   11.276%   $36.276   $36.28   $36.30   $36.30  
  Purchase #6 $139.39   8.803%   $151.6605   $151.66   $151.65   $151.70  
  Purchase #7 $233.63   5.568%   $246.6385   $246.64   $246.65   $246.60  
  7 purchase totals = $1,055.19       $1,153.1172   $1,153.12   $1,153.15   $1,153.10