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 $68.61   7.622%   $73.8395   $73.84   $73.85   $73.80  
  Purchase #2 $211.62   11.298%   $235.5288   $235.53   $235.55   $235.50  
  Purchase #3 $44.33   12.255%   $49.7626   $49.76   $49.75   $49.80  
  Purchase #4 $182.37   5.126%   $191.7183   $191.72   $191.70   $191.70  
  Purchase #5 $14.70   12.510%   $16.539   $16.54   $16.55   $16.50  
  Purchase #6 $190.94   6.486%   $203.3244   $203.32   $203.30   $203.30  
  Purchase #7 $235.92   8.629%   $256.2775   $256.28   $256.30   $256.30  
  7 purchase totals = $948.49       $1,026.9901   $1,026.99   $1,027.00   $1,026.90