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 $98.67   13.529%   $112.0191   $112.02   $112.00   $112.00  
  Purchase #2 $237.73   7.345%   $255.1913   $255.19   $255.20   $255.20  
  Purchase #3 $43.73   7.252%   $46.9013   $46.90   $46.90   $46.90  
  Purchase #4 $117.65   7.696%   $126.7043   $126.70   $126.70   $126.70  
  Purchase #5 $246.74   12.102%   $276.6005   $276.60   $276.60   $276.60  
  Purchase #6 $29.74   9.265%   $32.4954   $32.50   $32.50   $32.50  
  Purchase #7 $222.96   5.174%   $234.496   $234.50   $234.50   $234.50  
  7 purchase totals = $997.22       $1,084.4079   $1,084.41   $1,084.40   $1,084.40