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 $151.62   11.823%   $169.546   $169.55   $169.55   $169.50  
  Purchase #2 $71.40   10.195%   $78.6792   $78.68   $78.70   $78.70  
  Purchase #3 $29.57   8.213%   $31.9986   $32.00   $32.00   $32.00  
  Purchase #4 $73.88   3.864%   $76.7347   $76.73   $76.75   $76.70  
  Purchase #5 $185.56   13.698%   $210.978   $210.98   $211.00   $211.00  
  Purchase #6 $127.43   4.275%   $132.8776   $132.88   $132.90   $132.90  
  Purchase #7 $174.41   13.384%   $197.753   $197.75   $197.75   $197.80  
  7 purchase totals = $813.87       $898.5671   $898.57   $898.65   $898.60