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 $67.54   12.164%   $75.7556   $75.76   $75.75   $75.80  
  Purchase #2 $172.80   4.354%   $180.3237   $180.32   $180.30   $180.30  
  Purchase #3 $166.84   5.454%   $175.9395   $175.94   $175.95   $175.90  
  Purchase #4 $166.39   4.588%   $174.024   $174.02   $174.00   $174.00  
  Purchase #5 $205.55   7.820%   $221.624   $221.62   $221.60   $221.60  
  Purchase #6 $136.42   13.223%   $154.4588   $154.46   $154.45   $154.50  
  Purchase #7 $105.78   6.630%   $112.7932   $112.79   $112.80   $112.80  
  7 purchase totals = $1,021.32       $1,094.9188   $1,094.91   $1,094.85   $1,094.90