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 $92.63   11.840%   $103.5974   $103.60   $103.60   $103.60  
  Purchase #2 $132.86   6.627%   $141.6646   $141.66   $141.65   $141.70  
  Purchase #3 $96.80   11.127%   $107.5709   $107.57   $107.55   $107.60  
  Purchase #4 $119.62   5.630%   $126.3546   $126.35   $126.35   $126.40  
  Purchase #5 $147.31   9.124%   $160.7506   $160.75   $160.75   $160.80  
  Purchase #6 $146.80   7.162%   $157.3138   $157.31   $157.30   $157.30  
  Purchase #7 $61.55   5.710%   $65.0645   $65.06   $65.05   $65.10  
  7 purchase totals = $797.57       $862.3164   $862.30   $862.25   $862.50