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 $150.48   7.672%   $162.0248   $162.02   $162.00   $162.00  
  Purchase #2 $148.67   8.425%   $161.1954   $161.20   $161.20   $161.20  
  Purchase #3 $99.70   3.674%   $103.363   $103.36   $103.35   $103.40  
  Purchase #4 $31.43   8.158%   $33.9941   $33.99   $34.00   $34.00  
  Purchase #5 $97.66   9.192%   $106.6369   $106.64   $106.65   $106.60  
  Purchase #6 $212.43   6.549%   $226.342   $226.34   $226.35   $226.30  
  Purchase #7 $162.62   3.859%   $168.8955   $168.90   $168.90   $168.90  
  7 purchase totals = $902.99       $962.4517   $962.45   $962.45   $962.40