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 $43.99   7.360%   $47.2277   $47.23   $47.25   $47.20  
  Purchase #2 $244.96   9.670%   $268.6476   $268.65   $268.65   $268.60  
  Purchase #3 $95.39   8.241%   $103.2511   $103.25   $103.25   $103.30  
  Purchase #4 $250.87   4.636%   $262.5003   $262.50   $262.50   $262.50  
  Purchase #5 $114.82   6.613%   $122.413   $122.41   $122.40   $122.40  
  Purchase #6 $11.85   6.334%   $12.6006   $12.60   $12.60   $12.60  
  Purchase #7 $211.90   12.327%   $238.0209   $238.02   $238.00   $238.00  
  7 purchase totals = $973.78       $1,054.6612   $1,054.66   $1,054.65   $1,054.60