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 $87.56   8.515%   $95.0157   $95.02   $95.00   $95.00  
  Purchase #2 $187.25   6.237%   $198.9288   $198.93   $198.95   $198.90  
  Purchase #3 $75.44   4.547%   $78.8703   $78.87   $78.85   $78.90  
  Purchase #4 $18.78   12.384%   $21.1057   $21.11   $21.10   $21.10  
  Purchase #5 $192.71   8.437%   $208.9689   $208.97   $208.95   $209.00  
  Purchase #6 $169.51   3.607%   $175.6242   $175.62   $175.60   $175.60  
  Purchase #7 $248.69   13.539%   $282.3601   $282.36   $282.35   $282.40  
  7 purchase totals = $979.94       $1,060.8737   $1,060.88   $1,060.80   $1,060.90