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 $59.27   8.448%   $64.2771   $64.28   $64.30   $64.30  
  Purchase #2 $93.42   13.142%   $105.6973   $105.70   $105.70   $105.70  
  Purchase #3 $158.32   7.720%   $170.5423   $170.54   $170.55   $170.50  
  Purchase #4 $198.77   7.155%   $212.992   $212.99   $213.00   $213.00  
  Purchase #5 $114.85   8.310%   $124.394   $124.39   $124.40   $124.40  
  Purchase #6 $244.32   13.141%   $276.4261   $276.43   $276.45   $276.40  
  Purchase #7 $126.69   11.567%   $141.3442   $141.34   $141.35   $141.30  
  7 purchase totals = $995.64       $1,095.6730   $1,095.67   $1,095.75   $1,095.60