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 $55.84   13.454%   $63.3527   $63.35   $63.35   $63.40  
  Purchase #2 $156.59   3.552%   $162.1521   $162.15   $162.15   $162.20  
  Purchase #3 $168.94   10.247%   $186.2513   $186.25   $186.25   $186.30  
  Purchase #4 $248.78   3.239%   $256.838   $256.84   $256.85   $256.80  
  Purchase #5 $178.34   13.525%   $202.4605   $202.46   $202.45   $202.50  
  Purchase #6 $192.38   9.741%   $211.1197   $211.12   $211.10   $211.10  
  Purchase #7 $73.27   3.162%   $75.5868   $75.59   $75.60   $75.60  
  7 purchase totals = $1,074.14       $1,157.7611   $1,157.76   $1,157.75   $1,157.90