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 $58.48   7.740%   $63.0064   $63.01   $63.00   $63.00  
  Purchase #2 $49.37   11.338%   $54.9676   $54.97   $54.95   $55.00  
  Purchase #3 $22.48   6.755%   $23.9985   $24.00   $24.00   $24.00  
  Purchase #4 $64.40   10.703%   $71.2927   $71.29   $71.30   $71.30  
  Purchase #5 $78.87   4.784%   $82.6431   $82.64   $82.65   $82.60  
  Purchase #6 $100.57   13.827%   $114.4758   $114.48   $114.50   $114.50  
  Purchase #7 $225.34   10.596%   $249.217   $249.22   $249.20   $249.20  
  7 purchase totals = $599.51       $659.6011   $659.61   $659.60   $659.60