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 $41.56   11.518%   $46.3469   $46.35   $46.35   $46.30  
  Purchase #2 $192.67   3.721%   $199.8393   $199.84   $199.85   $199.80  
  Purchase #3 $92.26   3.331%   $95.3332   $95.33   $95.35   $95.30  
  Purchase #4 $215.72   4.583%   $225.6064   $225.61   $225.60   $225.60  
  Purchase #5 $63.46   9.127%   $69.252   $69.25   $69.25   $69.30  
  Purchase #6 $235.63   11.301%   $262.2585   $262.26   $262.25   $262.30  
  Purchase #7 $215.39   4.318%   $224.6905   $224.69   $224.70   $224.70  
  7 purchase totals = $1,056.69       $1,123.3268   $1,123.33   $1,123.35   $1,123.30