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 $61.84   10.408%   $68.2763   $68.28   $68.30   $68.30  
  Purchase #2 $85.77   7.685%   $92.3614   $92.36   $92.35   $92.40  
  Purchase #3 $9.52   8.768%   $10.3547   $10.35   $10.35   $10.40  
  Purchase #4 $229.27   7.779%   $247.1049   $247.10   $247.10   $247.10  
  Purchase #5 $225.38   3.528%   $233.3314   $233.33   $233.35   $233.30  
  Purchase #6 $248.36   4.531%   $259.6132   $259.61   $259.60   $259.60  
  Purchase #7 $176.30   4.533%   $184.2917   $184.29   $184.30   $184.30  
  7 purchase totals = $1,036.44       $1,095.3336   $1,095.32   $1,095.35   $1,095.40