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 $176.63   11.543%   $197.0184   $197.02   $197.00   $197.00  
  Purchase #2 $199.37   4.338%   $208.0187   $208.02   $208.00   $208.00  
  Purchase #3 $140.87   8.532%   $152.889   $152.89   $152.90   $152.90  
  Purchase #4 $235.59   3.425%   $243.659   $243.66   $243.65   $243.70  
  Purchase #5 $80.68   11.273%   $89.7751   $89.78   $89.80   $89.80  
  Purchase #6 $179.83   8.239%   $194.6462   $194.65   $194.65   $194.60  
  Purchase #7 $22.79   6.316%   $24.2294   $24.23   $24.25   $24.20  
  7 purchase totals = $1,035.76       $1,110.2358   $1,110.25   $1,110.25   $1,110.20