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 $56.49   11.796%   $63.1536   $63.15   $63.15   $63.20  
  Purchase #2 $211.43   4.871%   $221.7288   $221.73   $221.75   $221.70  
  Purchase #3 $144.57   9.549%   $158.375   $158.38   $158.40   $158.40  
  Purchase #4 $240.51   6.496%   $256.1335   $256.13   $256.15   $256.10  
  Purchase #5 $130.57   4.588%   $136.5606   $136.56   $136.55   $136.60  
  Purchase #6 $140.85   13.599%   $160.0042   $160.00   $160.00   $160.00  
  Purchase #7 $199.80   6.549%   $212.8849   $212.88   $212.90   $212.90  
  7 purchase totals = $1,124.22       $1,208.8406   $1,208.83   $1,208.90   $1,208.90