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 $174.77   6.517%   $186.1598   $186.16   $186.15   $186.20  
  Purchase #2 $211.38   3.558%   $218.9009   $218.90   $218.90   $218.90  
  Purchase #3 $214.37   8.244%   $232.0427   $232.04   $232.05   $232.00  
  Purchase #4 $237.57   10.699%   $262.9876   $262.99   $263.00   $263.00  
  Purchase #5 $228.83   7.786%   $246.6467   $246.65   $246.65   $246.60  
  Purchase #6 $183.77   13.786%   $209.1045   $209.10   $209.10   $209.10  
  Purchase #7 $146.81   6.505%   $156.36   $156.36   $156.35   $156.40  
  7 purchase totals = $1,397.50       $1,512.2022   $1,512.20   $1,512.20   $1,512.20