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 $72.71   12.737%   $81.9711   $81.97   $81.95   $82.00  
  Purchase #2 $130.94   4.837%   $137.2736   $137.27   $137.25   $137.30  
  Purchase #3 $150.72   6.616%   $160.6916   $160.69   $160.70   $160.70  
  Purchase #4 $214.73   9.611%   $235.3677   $235.37   $235.35   $235.40  
  Purchase #5 $163.98   7.302%   $175.9538   $175.95   $175.95   $176.00  
  Purchase #6 $124.64   6.104%   $132.248   $132.25   $132.25   $132.20  
  Purchase #7 $169.96   7.809%   $183.2322   $183.23   $183.25   $183.20  
  7 purchase totals = $1,027.68       $1,106.7380   $1,106.73   $1,106.70   $1,106.80