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 $64.94   13.495%   $73.7037   $73.70   $73.70   $73.70  
  Purchase #2 $71.58   3.383%   $74.0016   $74.00   $74.00   $74.00  
  Purchase #3 $74.70   10.114%   $82.2552   $82.26   $82.25   $82.30  
  Purchase #4 $152.65   11.366%   $170.0002   $170.00   $170.00   $170.00  
  Purchase #5 $236.66   7.620%   $254.6935   $254.69   $254.70   $254.70  
  Purchase #6 $149.34   9.211%   $163.0957   $163.10   $163.10   $163.10  
  Purchase #7 $59.72   13.309%   $67.6681   $67.67   $67.65   $67.70  
  7 purchase totals = $809.59       $885.4180   $885.42   $885.40   $885.50