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 $162.27   6.385%   $172.6309   $172.63   $172.65   $172.60  
  Purchase #2 $177.70   13.657%   $201.9685   $201.97   $201.95   $202.00  
  Purchase #3 $173.73   6.146%   $184.4074   $184.41   $184.40   $184.40  
  Purchase #4 $32.96   6.578%   $35.1281   $35.13   $35.15   $35.10  
  Purchase #5 $180.26   7.678%   $194.1004   $194.10   $194.10   $194.10  
  Purchase #6 $23.60   12.502%   $26.5505   $26.55   $26.55   $26.60  
  Purchase #7 $188.45   10.765%   $208.7366   $208.74   $208.75   $208.70  
  7 purchase totals = $938.97       $1,023.5224   $1,023.53   $1,023.55   $1,023.50