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 $61.92   11.732%   $69.1845   $69.18   $69.20   $69.20  
  Purchase #2 $214.83   10.700%   $237.8168   $237.82   $237.80   $237.80  
  Purchase #3 $77.42   12.279%   $86.9264   $86.93   $86.95   $86.90  
  Purchase #4 $64.77   9.590%   $70.9814   $70.98   $71.00   $71.00  
  Purchase #5 $189.68   5.370%   $199.8658   $199.87   $199.85   $199.90  
  Purchase #6 $155.76   3.534%   $161.2646   $161.26   $161.25   $161.30  
  Purchase #7 $104.60   9.227%   $114.2514   $114.25   $114.25   $114.30  
  7 purchase totals = $868.98       $940.2909   $940.29   $940.30   $940.40