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 $86.66   8.844%   $94.3242   $94.32   $94.30   $94.30  
  Purchase #2 $210.37   5.639%   $222.2328   $222.23   $222.25   $222.20  
  Purchase #3 $144.74   3.192%   $149.3601   $149.36   $149.35   $149.40  
  Purchase #4 $117.93   3.689%   $122.2804   $122.28   $122.30   $122.30  
  Purchase #5 $202.92   3.572%   $210.1683   $210.17   $210.15   $210.20  
  Purchase #6 $167.30   9.529%   $183.242   $183.24   $183.25   $183.20  
  Purchase #7 $180.28   7.528%   $193.8515   $193.85   $193.85   $193.90  
  7 purchase totals = $1,110.20       $1,175.4593   $1,175.45   $1,175.45   $1,175.50