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 $195.71   3.853%   $203.2507   $203.25   $203.25   $203.30  
  Purchase #2 $209.91   4.807%   $220.0004   $220.00   $220.00   $220.00  
  Purchase #3 $55.70   5.721%   $58.8866   $58.89   $58.90   $58.90  
  Purchase #4 $170.41   3.659%   $176.6453   $176.65   $176.65   $176.60  
  Purchase #5 $146.83   4.394%   $153.2817   $153.28   $153.30   $153.30  
  Purchase #6 $214.73   3.480%   $222.2026   $222.20   $222.20   $222.20  
  Purchase #7 $84.64   12.716%   $95.4028   $95.40   $95.40   $95.40  
  7 purchase totals = $1,077.93       $1,129.6701   $1,129.67   $1,129.70   $1,129.70