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 $177.31   11.219%   $197.2024   $197.20   $197.20   $197.20  
  Purchase #2 $193.93   8.124%   $209.6849   $209.68   $209.70   $209.70  
  Purchase #3 $21.56   5.543%   $22.7551   $22.76   $22.75   $22.80  
  Purchase #4 $192.94   13.575%   $219.1316   $219.13   $219.15   $219.10  
  Purchase #5 $236.65   3.804%   $245.6522   $245.65   $245.65   $245.70  
  Purchase #6 $192.51   11.493%   $214.6352   $214.64   $214.65   $214.60  
  Purchase #7 $134.90   4.770%   $141.3347   $141.33   $141.35   $141.30  
  7 purchase totals = $1,149.80       $1,250.3961   $1,250.39   $1,250.45   $1,250.40