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 $73.52   11.548%   $82.0101   $82.01   $82.00   $82.00  
  Purchase #2 $239.93   3.842%   $249.1481   $249.15   $249.15   $249.10  
  Purchase #3 $239.57   5.703%   $253.2327   $253.23   $253.25   $253.20  
  Purchase #4 $221.92   7.421%   $238.3887   $238.39   $238.40   $238.40  
  Purchase #5 $157.65   9.515%   $172.6504   $172.65   $172.65   $172.70  
  Purchase #6 $166.89   11.241%   $185.6501   $185.65   $185.65   $185.70  
  Purchase #7 $178.41   3.430%   $184.5295   $184.53   $184.55   $184.50  
  7 purchase totals = $1,277.89       $1,365.6096   $1,365.61   $1,365.65   $1,365.60