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 $244.88   8.461%   $265.5993   $265.60   $265.60   $265.60  
  Purchase #2 $193.64   4.282%   $201.9317   $201.93   $201.95   $201.90  
  Purchase #3 $105.35   7.295%   $113.0353   $113.04   $113.05   $113.00  
  Purchase #4 $205.87   10.285%   $227.0437   $227.04   $227.05   $227.00  
  Purchase #5 $46.30   5.745%   $48.9599   $48.96   $48.95   $49.00  
  Purchase #6 $239.86   10.377%   $264.7503   $264.75   $264.75   $264.80  
  Purchase #7 $57.50   5.517%   $60.6723   $60.67   $60.65   $60.70  
  7 purchase totals = $1,093.40       $1,181.9925   $1,181.99   $1,182.00   $1,182.00