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 $44.73   4.621%   $46.797   $46.80   $46.80   $46.80  
  Purchase #2 $180.96   13.828%   $205.9831   $205.98   $206.00   $206.00  
  Purchase #3 $113.93   4.679%   $119.2608   $119.26   $119.25   $119.30  
  Purchase #4 $249.37   10.405%   $275.3169   $275.32   $275.30   $275.30  
  Purchase #5 $29.29   5.598%   $30.9297   $30.93   $30.95   $30.90  
  Purchase #6 $239.85   6.608%   $255.6993   $255.70   $255.70   $255.70  
  Purchase #7 $248.75   7.852%   $268.2819   $268.28   $268.30   $268.30  
  7 purchase totals = $1,106.88       $1,202.2687   $1,202.27   $1,202.30   $1,202.30