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 $92.28   3.146%   $95.1831   $95.18   $95.20   $95.20  
  Purchase #2 $78.37   10.197%   $86.3614   $86.36   $86.35   $86.40  
  Purchase #3 $215.93   11.861%   $241.5415   $241.54   $241.55   $241.50  
  Purchase #4 $179.47   6.261%   $190.7066   $190.71   $190.70   $190.70  
  Purchase #5 $105.66   7.542%   $113.6289   $113.63   $113.65   $113.60  
  Purchase #6 $243.82   13.792%   $277.4477   $277.45   $277.45   $277.40  
  Purchase #7 $109.91   9.559%   $120.4163   $120.42   $120.40   $120.40  
  7 purchase totals = $1,025.44       $1,125.2855   $1,125.29   $1,125.30   $1,125.20