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 $69.67   3.677%   $72.2318   $72.23   $72.25   $72.20  
  Purchase #2 $193.42   5.114%   $203.3115   $203.31   $203.30   $203.30  
  Purchase #3 $212.33   11.763%   $237.3064   $237.31   $237.30   $237.30  
  Purchase #4 $40.36   8.793%   $43.9089   $43.91   $43.90   $43.90  
  Purchase #5 $217.25   12.202%   $243.7588   $243.76   $243.75   $243.80  
  Purchase #6 $160.33   3.819%   $166.453   $166.45   $166.45   $166.50  
  Purchase #7 $70.33   9.624%   $77.0986   $77.10   $77.10   $77.10  
  7 purchase totals = $963.69       $1,044.0690   $1,044.07   $1,044.05   $1,044.10