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 $61.62   7.477%   $66.2273   $66.23   $66.25   $66.20  
  Purchase #2 $202.55   8.180%   $219.1186   $219.12   $219.10   $219.10  
  Purchase #3 $17.63   9.745%   $19.348   $19.35   $19.35   $19.30  
  Purchase #4 $242.59   7.737%   $261.3592   $261.36   $261.35   $261.40  
  Purchase #5 $176.83   11.110%   $196.4758   $196.48   $196.50   $196.50  
  Purchase #6 $130.31   11.760%   $145.6345   $145.63   $145.65   $145.60  
  Purchase #7 $101.88   4.750%   $106.7193   $106.72   $106.70   $106.70  
  7 purchase totals = $933.41       $1,014.8827   $1,014.89   $1,014.90   $1,014.80