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 $94.44   8.694%   $102.6506   $102.65   $102.65   $102.70  
  Purchase #2 $60.97   8.218%   $65.9805   $65.98   $66.00   $66.00  
  Purchase #3 $197.56   5.666%   $208.7537   $208.75   $208.75   $208.80  
  Purchase #4 $225.47   3.636%   $233.6681   $233.67   $233.65   $233.70  
  Purchase #5 $94.84   3.301%   $97.9707   $97.97   $97.95   $98.00  
  Purchase #6 $241.72   11.475%   $269.4574   $269.46   $269.45   $269.50  
  Purchase #7 $197.70   8.652%   $214.805   $214.81   $214.80   $214.80  
  7 purchase totals = $1,112.70       $1,193.2860   $1,193.29   $1,193.25   $1,193.50