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 $157.25   6.243%   $167.0671   $167.07   $167.05   $167.10  
  Purchase #2 $46.86   5.373%   $49.3778   $49.38   $49.40   $49.40  
  Purchase #3 $212.54   8.656%   $230.9375   $230.94   $230.95   $230.90  
  Purchase #4 $149.54   8.583%   $162.375   $162.38   $162.40   $162.40  
  Purchase #5 $40.44   9.709%   $44.3663   $44.37   $44.35   $44.40  
  Purchase #6 $207.81   7.538%   $223.4747   $223.47   $223.45   $223.50  
  Purchase #7 $226.61   8.767%   $246.4769   $246.48   $246.50   $246.50  
  7 purchase totals = $1,041.05       $1,124.0753   $1,124.09   $1,124.10   $1,124.20