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 $213.90   5.533%   $225.7351   $225.74   $225.75   $225.70  
  Purchase #2 $202.79   10.602%   $224.2898   $224.29   $224.30   $224.30  
  Purchase #3 $153.57   5.114%   $161.4236   $161.42   $161.40   $161.40  
  Purchase #4 $30.30   9.741%   $33.2515   $33.25   $33.25   $33.30  
  Purchase #5 $137.70   3.516%   $142.5415   $142.54   $142.55   $142.50  
  Purchase #6 $184.42   5.608%   $194.7623   $194.76   $194.75   $194.80  
  Purchase #7 $68.48   12.389%   $76.964   $76.96   $76.95   $77.00  
  7 purchase totals = $991.16       $1,058.9678   $1,058.96   $1,058.95   $1,059.00