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 $113.40   10.723%   $125.5599   $125.56   $125.55   $125.60  
  Purchase #2 $180.51   9.357%   $197.4003   $197.40   $197.40   $197.40  
  Purchase #3 $214.85   6.400%   $228.6004   $228.60   $228.60   $228.60  
  Purchase #4 $243.37   13.297%   $275.7309   $275.73   $275.75   $275.70  
  Purchase #5 $16.44   12.831%   $18.5494   $18.55   $18.55   $18.50  
  Purchase #6 $87.64   9.133%   $95.6442   $95.64   $95.65   $95.60  
  Purchase #7 $162.92   9.258%   $178.0031   $178.00   $178.00   $178.00  
  7 purchase totals = $1,019.13       $1,119.4882   $1,119.48   $1,119.50   $1,119.40