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 $183.76   7.285%   $197.1469   $197.15   $197.15   $197.10  
  Purchase #2 $238.35   4.181%   $248.3154   $248.32   $248.30   $248.30  
  Purchase #3 $73.79   11.219%   $82.0685   $82.07   $82.05   $82.10  
  Purchase #4 $18.68   10.621%   $20.664   $20.66   $20.65   $20.70  
  Purchase #5 $101.76   6.162%   $108.0305   $108.03   $108.05   $108.00  
  Purchase #6 $83.92   13.278%   $95.0629   $95.06   $95.05   $95.10  
  Purchase #7 $249.99   8.364%   $270.8992   $270.90   $270.90   $270.90  
  7 purchase totals = $950.25       $1,022.1874   $1,022.19   $1,022.15   $1,022.20