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 $216.69   9.514%   $237.3059   $237.31   $237.30   $237.30  
  Purchase #2 $170.98   7.788%   $184.2959   $184.30   $184.30   $184.30  
  Purchase #3 $21.77   3.473%   $22.5261   $22.53   $22.55   $22.50  
  Purchase #4 $56.60   4.665%   $59.2404   $59.24   $59.25   $59.20  
  Purchase #5 $44.82   9.495%   $49.0757   $49.08   $49.10   $49.10  
  Purchase #6 $210.38   7.406%   $225.9607   $225.96   $225.95   $226.00  
  Purchase #7 $7.30   4.540%   $7.6314   $7.63   $7.65   $7.60  
  7 purchase totals = $728.54       $786.0361   $786.05   $786.10   $786.00