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 $174.32   4.662%   $182.4468   $182.45   $182.45   $182.40  
  Purchase #2 $208.65   4.253%   $217.5239   $217.52   $217.50   $217.50  
  Purchase #3 $243.35   10.322%   $268.4686   $268.47   $268.45   $268.50  
  Purchase #4 $147.77   11.318%   $164.4946   $164.49   $164.50   $164.50  
  Purchase #5 $87.86   3.629%   $91.0484   $91.05   $91.05   $91.00  
  Purchase #6 $159.53   12.234%   $179.0469   $179.05   $179.05   $179.00  
  Purchase #7 $57.59   4.256%   $60.041   $60.04   $60.05   $60.00  
  7 purchase totals = $1,079.07       $1,163.0702   $1,163.07   $1,163.05   $1,162.90