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 $68.64   7.722%   $73.9404   $73.94   $73.95   $73.90  
  Purchase #2 $146.36   8.770%   $159.1958   $159.20   $159.20   $159.20  
  Purchase #3 $181.53   3.372%   $187.6512   $187.65   $187.65   $187.70  
  Purchase #4 $189.26   8.641%   $205.614   $205.61   $205.60   $205.60  
  Purchase #5 $234.85   12.264%   $263.652   $263.65   $263.65   $263.70  
  Purchase #6 $114.55   13.593%   $130.1208   $130.12   $130.10   $130.10  
  Purchase #7 $108.35   10.560%   $119.7918   $119.79   $119.80   $119.80  
  7 purchase totals = $1,043.54       $1,139.9660   $1,139.96   $1,139.95   $1,140.00