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 $87.95   9.422%   $96.2366   $96.24   $96.25   $96.20  
  Purchase #2 $143.41   10.381%   $158.2974   $158.30   $158.30   $158.30  
  Purchase #3 $100.96   12.200%   $113.2771   $113.28   $113.30   $113.30  
  Purchase #4 $177.65   3.233%   $183.3934   $183.39   $183.40   $183.40  
  Purchase #5 $184.88   6.340%   $196.6014   $196.60   $196.60   $196.60  
  Purchase #6 $175.35   6.621%   $186.9599   $186.96   $186.95   $187.00  
  Purchase #7 $170.50   9.215%   $186.2116   $186.21   $186.20   $186.20  
  7 purchase totals = $1,040.70       $1,120.9774   $1,120.98   $1,121.00   $1,121.00