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 $84.90   11.733%   $94.8613   $94.86   $94.85   $94.90  
  Purchase #2 $206.67   9.432%   $226.1631   $226.16   $226.15   $226.20  
  Purchase #3 $90.44   6.620%   $96.4271   $96.43   $96.45   $96.40  
  Purchase #4 $107.34   8.789%   $116.7741   $116.77   $116.75   $116.80  
  Purchase #5 $44.36   4.811%   $46.4942   $46.49   $46.50   $46.50  
  Purchase #6 $186.43   11.392%   $207.6681   $207.67   $207.65   $207.70  
  Purchase #7 $248.99   6.462%   $265.0797   $265.08   $265.10   $265.10  
  7 purchase totals = $969.13       $1,053.4676   $1,053.46   $1,053.45   $1,053.60