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 $179.37   9.548%   $196.4962   $196.50   $196.50   $196.50  
  Purchase #2 $29.38   4.548%   $30.7162   $30.72   $30.70   $30.70  
  Purchase #3 $81.40   8.322%   $88.1741   $88.17   $88.15   $88.20  
  Purchase #4 $17.62   5.349%   $18.5625   $18.56   $18.55   $18.60  
  Purchase #5 $44.94   7.458%   $48.2916   $48.29   $48.30   $48.30  
  Purchase #6 $232.99   3.852%   $241.9648   $241.96   $241.95   $242.00  
  Purchase #7 $75.52   7.806%   $81.4151   $81.42   $81.40   $81.40  
  7 purchase totals = $661.22       $705.6205   $705.62   $705.55   $705.70