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 $61.85   11.594%   $69.0209   $69.02   $69.00   $69.00  
  Purchase #2 $174.51   8.591%   $189.5022   $189.50   $189.50   $189.50  
  Purchase #3 $13.29   7.203%   $14.2473   $14.25   $14.25   $14.20  
  Purchase #4 $143.79   13.118%   $162.6524   $162.65   $162.65   $162.70  
  Purchase #5 $206.57   4.673%   $216.223   $216.22   $216.20   $216.20  
  Purchase #6 $118.58   12.364%   $133.2412   $133.24   $133.25   $133.20  
  Purchase #7 $133.35   4.722%   $139.6468   $139.65   $139.65   $139.60  
  7 purchase totals = $851.94       $924.5338   $924.53   $924.50   $924.40