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 $87.95   9.558%   $96.3563   $96.36   $96.35   $96.40  
  Purchase #2 $32.29   12.190%   $36.2262   $36.23   $36.25   $36.20  
  Purchase #3 $181.37   5.562%   $191.4578   $191.46   $191.45   $191.50  
  Purchase #4 $101.25   4.721%   $106.03   $106.03   $106.05   $106.00  
  Purchase #5 $213.32   10.272%   $235.2322   $235.23   $235.25   $235.20  
  Purchase #6 $177.27   6.315%   $188.4646   $188.46   $188.45   $188.50  
  Purchase #7 $221.29   13.870%   $251.9829   $251.98   $252.00   $252.00  
  7 purchase totals = $1,014.74       $1,105.7500   $1,105.75   $1,105.80   $1,105.80