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 $211.83   12.243%   $237.7643   $237.76   $237.75   $237.80  
  Purchase #2 $196.40   11.624%   $219.2295   $219.23   $219.25   $219.20  
  Purchase #3 $225.43   8.498%   $244.587   $244.59   $244.60   $244.60  
  Purchase #4 $27.27   9.318%   $29.811   $29.81   $29.80   $29.80  
  Purchase #5 $150.93   6.237%   $160.3435   $160.34   $160.35   $160.30  
  Purchase #6 $243.33   9.416%   $266.242   $266.24   $266.25   $266.20  
  Purchase #7 $173.76   11.860%   $194.3679   $194.37   $194.35   $194.40  
  7 purchase totals = $1,228.95       $1,352.3452   $1,352.34   $1,352.35   $1,352.30