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 $86.78   10.854%   $96.1991   $96.20   $96.20   $96.20  
  Purchase #2 $240.91   12.666%   $271.4237   $271.42   $271.40   $271.40  
  Purchase #3 $10.58   9.779%   $11.6146   $11.61   $11.60   $11.60  
  Purchase #4 $211.46   9.695%   $231.961   $231.96   $231.95   $232.00  
  Purchase #5 $14.30   8.603%   $15.5302   $15.53   $15.55   $15.50  
  Purchase #6 $206.76   3.700%   $214.4101   $214.41   $214.40   $214.40  
  Purchase #7 $246.53   3.777%   $255.8414   $255.84   $255.85   $255.80  
  7 purchase totals = $1,017.32       $1,096.9801   $1,096.97   $1,096.95   $1,096.90