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 $204.82   13.745%   $232.9725   $232.97   $232.95   $233.00  
  Purchase #2 $248.42   4.409%   $259.3728   $259.37   $259.35   $259.40  
  Purchase #3 $154.34   5.674%   $163.0973   $163.10   $163.10   $163.10  
  Purchase #4 $60.47   12.760%   $68.186   $68.19   $68.20   $68.20  
  Purchase #5 $122.57   11.335%   $136.4633   $136.46   $136.45   $136.50  
  Purchase #6 $34.35   12.822%   $38.7544   $38.75   $38.75   $38.80  
  Purchase #7 $150.73   12.110%   $168.9834   $168.98   $169.00   $169.00  
  7 purchase totals = $975.70       $1,067.8297   $1,067.82   $1,067.80   $1,068.00