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 $124.32   6.280%   $132.1273   $132.13   $132.15   $132.10  
  Purchase #2 $59.69   9.387%   $65.2931   $65.29   $65.30   $65.30  
  Purchase #3 $236.85   5.802%   $250.592   $250.59   $250.60   $250.60  
  Purchase #4 $223.30   11.368%   $248.6847   $248.68   $248.70   $248.70  
  Purchase #5 $208.53   5.508%   $220.0158   $220.02   $220.00   $220.00  
  Purchase #6 $191.62   5.596%   $202.3431   $202.34   $202.35   $202.30  
  Purchase #7 $166.62   5.764%   $176.224   $176.22   $176.20   $176.20  
  7 purchase totals = $1,210.93       $1,295.2800   $1,295.27   $1,295.30   $1,295.20