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 $63.45   13.414%   $71.9612   $71.96   $71.95   $72.00  
  Purchase #2 $213.33   4.239%   $222.3731   $222.37   $222.35   $222.40  
  Purchase #3 $139.44   6.483%   $148.4799   $148.48   $148.50   $148.50  
  Purchase #4 $211.67   11.186%   $235.3474   $235.35   $235.35   $235.30  
  Purchase #5 $174.75   4.429%   $182.4897   $182.49   $182.50   $182.50  
  Purchase #6 $179.95   11.776%   $201.1409   $201.14   $201.15   $201.10  
  Purchase #7 $78.41   3.467%   $81.1285   $81.13   $81.15   $81.10  
  7 purchase totals = $1,061.00       $1,142.9207   $1,142.92   $1,142.95   $1,142.90