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 $173.71   13.137%   $196.5303   $196.53   $196.55   $196.50  
  Purchase #2 $82.73   4.826%   $86.7225   $86.72   $86.70   $86.70  
  Purchase #3 $182.92   4.505%   $191.1605   $191.16   $191.15   $191.20  
  Purchase #4 $66.25   12.268%   $74.3776   $74.38   $74.40   $74.40  
  Purchase #5 $235.51   4.604%   $246.3529   $246.35   $246.35   $246.40  
  Purchase #6 $144.92   11.265%   $161.2452   $161.25   $161.25   $161.20  
  Purchase #7 $209.87   4.264%   $218.8189   $218.82   $218.80   $218.80  
  7 purchase totals = $1,095.91       $1,175.2079   $1,175.21   $1,175.20   $1,175.20