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 $175.68   11.266%   $195.4721   $195.47   $195.45   $195.50  
  Purchase #2 $246.32   7.725%   $265.3482   $265.35   $265.35   $265.30  
  Purchase #3 $216.68   5.630%   $228.8791   $228.88   $228.90   $228.90  
  Purchase #4 $46.31   8.551%   $50.27   $50.27   $50.25   $50.30  
  Purchase #5 $196.50   6.520%   $209.3118   $209.31   $209.30   $209.30  
  Purchase #6 $178.78   5.419%   $188.4681   $188.47   $188.45   $188.50  
  Purchase #7 $23.85   13.153%   $26.987   $26.99   $27.00   $27.00  
  7 purchase totals = $1,084.12       $1,164.7363   $1,164.74   $1,164.70   $1,164.80