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 $112.66   5.207%   $118.5262   $118.53   $118.55   $118.50  
  Purchase #2 $210.40   11.685%   $234.9852   $234.99   $235.00   $235.00  
  Purchase #3 $145.26   4.418%   $151.6776   $151.68   $151.70   $151.70  
  Purchase #4 $42.80   6.795%   $45.7083   $45.71   $45.70   $45.70  
  Purchase #5 $193.80   11.597%   $216.275   $216.28   $216.30   $216.30  
  Purchase #6 $141.75   12.196%   $159.0378   $159.04   $159.05   $159.00  
  Purchase #7 $197.49   11.466%   $220.1342   $220.13   $220.15   $220.10  
  7 purchase totals = $1,044.16       $1,146.3443   $1,146.36   $1,146.45   $1,146.30