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 $62.95   7.511%   $67.6782   $67.68   $67.70   $67.70  
  Purchase #2 $86.42   13.702%   $98.2613   $98.26   $98.25   $98.30  
  Purchase #3 $191.62   13.419%   $217.3335   $217.33   $217.35   $217.30  
  Purchase #4 $195.67   5.540%   $206.5101   $206.51   $206.50   $206.50  
  Purchase #5 $240.57   6.134%   $255.3266   $255.33   $255.35   $255.30  
  Purchase #6 $234.88   7.506%   $252.5101   $252.51   $252.50   $252.50  
  Purchase #7 $70.96   10.690%   $78.5456   $78.55   $78.55   $78.50  
  7 purchase totals = $1,083.07       $1,176.1654   $1,176.17   $1,176.20   $1,176.10