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 $55.60   12.223%   $62.396   $62.40   $62.40   $62.40  
  Purchase #2 $13.78   3.748%   $14.2965   $14.30   $14.30   $14.30  
  Purchase #3 $89.31   4.481%   $93.312   $93.31   $93.30   $93.30  
  Purchase #4 $201.66   11.619%   $225.0909   $225.09   $225.10   $225.10  
  Purchase #5 $183.38   10.799%   $203.1832   $203.18   $203.20   $203.20  
  Purchase #6 $236.84   8.674%   $257.3835   $257.38   $257.40   $257.40  
  Purchase #7 $97.90   8.444%   $106.1667   $106.17   $106.15   $106.20  
  7 purchase totals = $878.47       $961.8288   $961.83   $961.85   $961.90