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 $86.53   10.157%   $95.3189   $95.32   $95.30   $95.30  
  Purchase #2 $235.77   5.209%   $248.0513   $248.05   $248.05   $248.10  
  Purchase #3 $164.85   7.753%   $177.6308   $177.63   $177.65   $177.60  
  Purchase #4 $20.29   12.221%   $22.7696   $22.77   $22.75   $22.80  
  Purchase #5 $163.69   5.283%   $172.3377   $172.34   $172.35   $172.30  
  Purchase #6 $240.34   7.265%   $257.8007   $257.80   $257.80   $257.80  
  Purchase #7 $140.76   7.695%   $151.5915   $151.59   $151.60   $151.60  
  7 purchase totals = $1,052.23       $1,125.5005   $1,125.50   $1,125.50   $1,125.50