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 $181.79   7.578%   $195.566   $195.57   $195.55   $195.60  
  Purchase #2 $117.38   5.604%   $123.958   $123.96   $123.95   $124.00  
  Purchase #3 $31.81   12.188%   $35.687   $35.69   $35.70   $35.70  
  Purchase #4 $228.44   4.705%   $239.1881   $239.19   $239.20   $239.20  
  Purchase #5 $164.79   6.498%   $175.4981   $175.50   $175.50   $175.50  
  Purchase #6 $178.57   11.348%   $198.8341   $198.83   $198.85   $198.80  
  Purchase #7 $124.47   3.308%   $128.5875   $128.59   $128.60   $128.60  
  7 purchase totals = $1,027.25       $1,097.3188   $1,097.33   $1,097.35   $1,097.40