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 $192.86   4.517%   $201.5715   $201.57   $201.55   $201.60  
  Purchase #2 $96.37   3.459%   $99.7034   $99.70   $99.70   $99.70  
  Purchase #3 $227.25   9.266%   $248.307   $248.31   $248.30   $248.30  
  Purchase #4 $129.55   5.544%   $136.7323   $136.73   $136.75   $136.70  
  Purchase #5 $163.80   6.273%   $174.0752   $174.08   $174.10   $174.10  
  Purchase #6 $217.71   5.421%   $229.5121   $229.51   $229.50   $229.50  
  Purchase #7 $174.65   6.379%   $185.7909   $185.79   $185.80   $185.80  
  7 purchase totals = $1,202.19       $1,275.6924   $1,275.69   $1,275.70   $1,275.70