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 $91.34   5.698%   $96.5446   $96.54   $96.55   $96.50  
  Purchase #2 $186.72   11.365%   $207.9407   $207.94   $207.95   $207.90  
  Purchase #3 $149.80   6.174%   $159.0487   $159.05   $159.05   $159.00  
  Purchase #4 $226.51   10.204%   $249.6231   $249.62   $249.60   $249.60  
  Purchase #5 $170.61   8.207%   $184.612   $184.61   $184.60   $184.60  
  Purchase #6 $119.91   6.701%   $127.9452   $127.95   $127.95   $127.90  
  Purchase #7 $158.53   11.572%   $176.8751   $176.88   $176.90   $176.90  
  7 purchase totals = $1,103.42       $1,202.5894   $1,202.59   $1,202.60   $1,202.40