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 $175.31   11.771%   $195.9457   $195.95   $195.95   $195.90  
  Purchase #2 $55.48   6.218%   $58.9297   $58.93   $58.95   $58.90  
  Purchase #3 $93.55   6.332%   $99.4736   $99.47   $99.45   $99.50  
  Purchase #4 $149.39   9.535%   $163.6343   $163.63   $163.65   $163.60  
  Purchase #5 $233.57   13.795%   $265.791   $265.79   $265.80   $265.80  
  Purchase #6 $186.42   5.461%   $196.6004   $196.60   $196.60   $196.60  
  Purchase #7 $76.52   8.605%   $83.1045   $83.10   $83.10   $83.10  
  7 purchase totals = $970.24       $1,063.4792   $1,063.47   $1,063.50   $1,063.40