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 $44.65   5.308%   $47.02   $47.02   $47.00   $47.00  
  Purchase #2 $175.44   12.871%   $198.0209   $198.02   $198.00   $198.00  
  Purchase #3 $141.68   4.695%   $148.3319   $148.33   $148.35   $148.30  
  Purchase #4 $48.77   3.702%   $50.5755   $50.58   $50.60   $50.60  
  Purchase #5 $232.87   9.374%   $254.6992   $254.70   $254.70   $254.70  
  Purchase #6 $174.40   13.120%   $197.2813   $197.28   $197.30   $197.30  
  Purchase #7 $114.71   3.542%   $118.773   $118.77   $118.75   $118.80  
  7 purchase totals = $932.52       $1,014.7018   $1,014.70   $1,014.70   $1,014.70