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 $218.42   8.640%   $237.2915   $237.29   $237.30   $237.30  
  Purchase #2 $246.70   6.449%   $262.6097   $262.61   $262.60   $262.60  
  Purchase #3 $120.41   6.750%   $128.5377   $128.54   $128.55   $128.50  
  Purchase #4 $211.68   5.581%   $223.4939   $223.49   $223.50   $223.50  
  Purchase #5 $188.68   3.617%   $195.5046   $195.50   $195.50   $195.50  
  Purchase #6 $131.29   8.271%   $142.149   $142.15   $142.15   $142.10  
  Purchase #7 $31.57   11.514%   $35.205   $35.21   $35.20   $35.20  
  7 purchase totals = $1,148.75       $1,224.7914   $1,224.79   $1,224.80   $1,224.70