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 $176.43   10.631%   $195.1863   $195.19   $195.20   $195.20  
  Purchase #2 $217.60   5.547%   $229.6703   $229.67   $229.65   $229.70  
  Purchase #3 $76.31   10.314%   $84.1806   $84.18   $84.20   $84.20  
  Purchase #4 $142.60   10.825%   $158.0365   $158.04   $158.05   $158.00  
  Purchase #5 $223.75   4.319%   $233.4138   $233.41   $233.40   $233.40  
  Purchase #6 $70.85   5.426%   $74.6943   $74.69   $74.70   $74.70  
  Purchase #7 $70.53   8.193%   $76.3085   $76.31   $76.30   $76.30  
  7 purchase totals = $978.07       $1,051.4903   $1,051.49   $1,051.50   $1,051.50