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 $41.54   5.380%   $43.7749   $43.77   $43.75   $43.80  
  Purchase #2 $64.86   5.263%   $68.2736   $68.27   $68.25   $68.30  
  Purchase #3 $150.39   4.863%   $157.7035   $157.70   $157.70   $157.70  
  Purchase #4 $145.46   10.619%   $160.9064   $160.91   $160.90   $160.90  
  Purchase #5 $157.48   12.737%   $177.5382   $177.54   $177.55   $177.50  
  Purchase #6 $201.86   12.680%   $227.4558   $227.46   $227.45   $227.50  
  Purchase #7 $192.49   4.344%   $200.8518   $200.85   $200.85   $200.90  
  7 purchase totals = $954.08       $1,036.5042   $1,036.50   $1,036.45   $1,036.60