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 $78.67   10.788%   $87.1569   $87.16   $87.15   $87.20  
  Purchase #2 $171.68   4.358%   $179.1618   $179.16   $179.15   $179.20  
  Purchase #3 $195.91   3.489%   $202.7453   $202.75   $202.75   $202.70  
  Purchase #4 $245.48   6.782%   $262.1285   $262.13   $262.15   $262.10  
  Purchase #5 $164.76   10.803%   $182.559   $182.56   $182.55   $182.60  
  Purchase #6 $147.68   9.524%   $161.745   $161.75   $161.75   $161.70  
  Purchase #7 $82.71   6.403%   $88.0059   $88.01   $88.00   $88.00  
  7 purchase totals = $1,086.89       $1,163.5024   $1,163.52   $1,163.50   $1,163.50