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 $69.54   9.237%   $75.9634   $75.96   $75.95   $76.00  
  Purchase #2 $249.75   5.312%   $263.0167   $263.02   $263.00   $263.00  
  Purchase #3 $152.76   7.371%   $164.0199   $164.02   $164.00   $164.00  
  Purchase #4 $151.93   12.280%   $170.587   $170.59   $170.60   $170.60  
  Purchase #5 $215.41   7.137%   $230.7838   $230.78   $230.80   $230.80  
  Purchase #6 $100.40   10.450%   $110.8918   $110.89   $110.90   $110.90  
  Purchase #7 $54.28   8.609%   $58.953   $58.95   $58.95   $59.00  
  7 purchase totals = $994.07       $1,074.2156   $1,074.21   $1,074.20   $1,074.30