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 $60.60   3.708%   $62.847   $62.85   $62.85   $62.80  
  Purchase #2 $163.69   12.666%   $184.423   $184.42   $184.40   $184.40  
  Purchase #3 $70.68   6.163%   $75.036   $75.04   $75.05   $75.00  
  Purchase #4 $226.95   10.510%   $250.8024   $250.80   $250.80   $250.80  
  Purchase #5 $142.81   11.559%   $159.3174   $159.32   $159.30   $159.30  
  Purchase #6 $58.32   11.439%   $64.9912   $64.99   $65.00   $65.00  
  Purchase #7 $201.57   9.333%   $220.3825   $220.38   $220.40   $220.40  
  7 purchase totals = $924.62       $1,017.7995   $1,017.80   $1,017.80   $1,017.70