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 $63.34   7.540%   $68.1158   $68.12   $68.10   $68.10  
  Purchase #2 $101.31   12.492%   $113.9656   $113.97   $113.95   $114.00  
  Purchase #3 $212.78   12.604%   $239.5988   $239.60   $239.60   $239.60  
  Purchase #4 $13.91   4.689%   $14.5622   $14.56   $14.55   $14.60  
  Purchase #5 $185.70   7.637%   $199.8819   $199.88   $199.90   $199.90  
  Purchase #6 $24.95   5.260%   $26.2624   $26.26   $26.25   $26.30  
  Purchase #7 $99.79   4.835%   $104.6148   $104.61   $104.60   $104.60  
  7 purchase totals = $701.78       $767.0015   $767.00   $766.95   $767.10