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 $105.92   7.644%   $114.0165   $114.02   $114.00   $114.00  
  Purchase #2 $114.84   4.162%   $119.6196   $119.62   $119.60   $119.60  
  Purchase #3 $146.28   3.726%   $151.7304   $151.73   $151.75   $151.70  
  Purchase #4 $221.48   8.631%   $240.5959   $240.60   $240.60   $240.60  
  Purchase #5 $153.78   6.570%   $163.8833   $163.88   $163.90   $163.90  
  Purchase #6 $167.74   12.673%   $188.9977   $189.00   $189.00   $189.00  
  Purchase #7 $34.39   13.273%   $38.9546   $38.95   $38.95   $39.00  
  7 purchase totals = $944.43       $1,017.7980   $1,017.80   $1,017.80   $1,017.80