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 $173.75   12.244%   $195.024   $195.02   $195.00   $195.00  
  Purchase #2 $182.89   8.621%   $198.6569   $198.66   $198.65   $198.70  
  Purchase #3 $44.41   13.111%   $50.2326   $50.23   $50.25   $50.20  
  Purchase #4 $210.97   11.206%   $234.6113   $234.61   $234.60   $234.60  
  Purchase #5 $134.32   3.581%   $139.13   $139.13   $139.15   $139.10  
  Purchase #6 $127.68   10.705%   $141.3481   $141.35   $141.35   $141.30  
  Purchase #7 $192.91   10.687%   $213.5263   $213.53   $213.55   $213.50  
  7 purchase totals = $1,066.93       $1,172.5292   $1,172.53   $1,172.55   $1,172.40