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 $167.48   9.137%   $182.7826   $182.78   $182.80   $182.80  
  Purchase #2 $148.63   13.261%   $168.3398   $168.34   $168.35   $168.30  
  Purchase #3 $69.67   8.207%   $75.3878   $75.39   $75.40   $75.40  
  Purchase #4 $200.25   7.650%   $215.5691   $215.57   $215.55   $215.60  
  Purchase #5 $176.95   13.819%   $201.4027   $201.40   $201.40   $201.40  
  Purchase #6 $127.90   8.158%   $138.3341   $138.33   $138.35   $138.30  
  Purchase #7 $153.98   13.525%   $174.8058   $174.81   $174.80   $174.80  
  7 purchase totals = $1,044.86       $1,156.6219   $1,156.62   $1,156.65   $1,156.60