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 $86.92   7.575%   $93.5042   $93.50   $93.50   $93.50  
  Purchase #2 $95.68   7.284%   $102.6493   $102.65   $102.65   $102.60  
  Purchase #3 $195.59   4.235%   $203.8732   $203.87   $203.85   $203.90  
  Purchase #4 $9.82   8.325%   $10.6375   $10.64   $10.65   $10.60  
  Purchase #5 $123.60   3.394%   $127.795   $127.80   $127.80   $127.80  
  Purchase #6 $136.80   6.267%   $145.3733   $145.37   $145.35   $145.40  
  Purchase #7 $227.61   3.439%   $235.4375   $235.44   $235.45   $235.40  
  7 purchase totals = $876.02       $919.2700   $919.27   $919.25   $919.20