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 $195.60   7.462%   $210.1957   $210.20   $210.20   $210.20  
  Purchase #2 $51.84   3.807%   $53.8135   $53.81   $53.80   $53.80  
  Purchase #3 $33.98   12.273%   $38.1504   $38.15   $38.15   $38.20  
  Purchase #4 $229.28   8.399%   $248.5372   $248.54   $248.55   $248.50  
  Purchase #5 $194.95   4.441%   $203.6077   $203.61   $203.60   $203.60  
  Purchase #6 $143.44   9.640%   $157.2676   $157.27   $157.25   $157.30  
  Purchase #7 $97.93   5.171%   $102.994   $102.99   $103.00   $103.00  
  7 purchase totals = $947.02       $1,014.5661   $1,014.57   $1,014.55   $1,014.60