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 $191.44   5.291%   $201.5691   $201.57   $201.55   $201.60  
  Purchase #2 $31.93   11.156%   $35.4921   $35.49   $35.50   $35.50  
  Purchase #3 $52.27   7.158%   $56.0115   $56.01   $56.00   $56.00  
  Purchase #4 $180.69   6.584%   $192.5866   $192.59   $192.60   $192.60  
  Purchase #5 $245.75   4.130%   $255.8995   $255.90   $255.90   $255.90  
  Purchase #6 $41.26   7.280%   $44.2637   $44.26   $44.25   $44.30  
  Purchase #7 $189.67   13.336%   $214.9644   $214.96   $214.95   $215.00  
  7 purchase totals = $933.01       $1,000.7869   $1,000.78   $1,000.75   $1,000.90