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 $60.56   11.628%   $67.6019   $67.60   $67.60   $67.60  
  Purchase #2 $108.54   6.813%   $115.9348   $115.93   $115.95   $115.90  
  Purchase #3 $220.33   9.456%   $241.1644   $241.16   $241.15   $241.20  
  Purchase #4 $245.45   6.813%   $262.1725   $262.17   $262.15   $262.20  
  Purchase #5 $101.72   12.846%   $114.787   $114.79   $114.80   $114.80  
  Purchase #6 $114.97   3.378%   $118.8537   $118.85   $118.85   $118.90  
  Purchase #7 $177.94   11.288%   $198.0259   $198.03   $198.05   $198.00  
  7 purchase totals = $1,029.51       $1,118.5402   $1,118.53   $1,118.55   $1,118.60