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 $184.47   5.197%   $194.0569   $194.06   $194.05   $194.10  
  Purchase #2 $33.87   8.398%   $36.7144   $36.71   $36.70   $36.70  
  Purchase #3 $133.73   8.745%   $145.4247   $145.42   $145.40   $145.40  
  Purchase #4 $248.61   7.760%   $267.9021   $267.90   $267.90   $267.90  
  Purchase #5 $54.40   4.162%   $56.6641   $56.66   $56.65   $56.70  
  Purchase #6 $118.27   8.139%   $127.896   $127.90   $127.90   $127.90  
  Purchase #7 $18.58   7.303%   $19.9369   $19.94   $19.95   $19.90  
  7 purchase totals = $791.93       $848.5951   $848.59   $848.55   $848.60