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 $241.58   10.150%   $266.1004   $266.10   $266.10   $266.10  
  Purchase #2 $183.30   4.542%   $191.6255   $191.63   $191.65   $191.60  
  Purchase #3 $247.43   13.606%   $281.0953   $281.10   $281.10   $281.10  
  Purchase #4 $208.69   4.363%   $217.7951   $217.80   $217.80   $217.80  
  Purchase #5 $221.60   4.755%   $232.1371   $232.14   $232.15   $232.10  
  Purchase #6 $151.94   3.186%   $156.7808   $156.78   $156.80   $156.80  
  Purchase #7 $119.62   8.118%   $129.3308   $129.33   $129.35   $129.30  
  7 purchase totals = $1,374.16       $1,474.8650   $1,474.88   $1,474.95   $1,474.80