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 $205.64   9.740%   $225.6693   $225.67   $225.65   $225.70  
  Purchase #2 $221.60   9.781%   $243.2747   $243.27   $243.25   $243.30  
  Purchase #3 $116.58   4.789%   $122.163   $122.16   $122.15   $122.20  
  Purchase #4 $127.46   4.117%   $132.7075   $132.71   $132.70   $132.70  
  Purchase #5 $164.33   13.685%   $186.8186   $186.82   $186.80   $186.80  
  Purchase #6 $44.67   9.451%   $48.8918   $48.89   $48.90   $48.90  
  Purchase #7 $95.39   7.532%   $102.5748   $102.57   $102.55   $102.60  
  7 purchase totals = $975.67       $1,062.0997   $1,062.09   $1,062.00   $1,062.20