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 $47.49   4.443%   $49.6   $49.60   $49.60   $49.60  
  Purchase #2 $212.98   11.609%   $237.7048   $237.70   $237.70   $237.70  
  Purchase #3 $140.57   4.829%   $147.3581   $147.36   $147.35   $147.40  
  Purchase #4 $182.63   11.799%   $204.1785   $204.18   $204.20   $204.20  
  Purchase #5 $84.36   10.632%   $93.3292   $93.33   $93.35   $93.30  
  Purchase #6 $239.46   3.731%   $248.3943   $248.39   $248.40   $248.40  
  Purchase #7 $47.76   11.375%   $53.1927   $53.19   $53.20   $53.20  
  7 purchase totals = $955.25       $1,033.7576   $1,033.75   $1,033.80   $1,033.80