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 $186.87   3.434%   $193.2871   $193.29   $193.30   $193.30  
  Purchase #2 $235.67   4.566%   $246.4307   $246.43   $246.45   $246.40  
  Purchase #3 $170.69   3.535%   $176.7239   $176.72   $176.70   $176.70  
  Purchase #4 $217.74   11.653%   $243.1132   $243.11   $243.10   $243.10  
  Purchase #5 $130.36   10.598%   $144.1756   $144.18   $144.20   $144.20  
  Purchase #6 $234.43   11.701%   $261.8607   $261.86   $261.85   $261.90  
  Purchase #7 $180.89   11.512%   $201.7141   $201.71   $201.70   $201.70  
  7 purchase totals = $1,356.65       $1,467.3053   $1,467.30   $1,467.30   $1,467.30