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 $174.94   12.109%   $196.1235   $196.12   $196.10   $196.10  
  Purchase #2 $60.38   3.757%   $62.6485   $62.65   $62.65   $62.60  
  Purchase #3 $185.58   8.136%   $200.6788   $200.68   $200.70   $200.70  
  Purchase #4 $79.41   3.272%   $82.0083   $82.01   $82.00   $82.00  
  Purchase #5 $147.58   9.752%   $161.972   $161.97   $161.95   $162.00  
  Purchase #6 $69.62   7.847%   $75.0831   $75.08   $75.10   $75.10  
  Purchase #7 $226.74   9.392%   $248.0354   $248.04   $248.05   $248.00  
  7 purchase totals = $944.25       $1,026.5496   $1,026.55   $1,026.55   $1,026.50