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 $58.66   5.385%   $61.8188   $61.82   $61.80   $61.80  
  Purchase #2 $72.29   5.174%   $76.0303   $76.03   $76.05   $76.00  
  Purchase #3 $16.97   5.416%   $17.8891   $17.89   $17.90   $17.90  
  Purchase #4 $157.92   9.505%   $172.9303   $172.93   $172.95   $172.90  
  Purchase #5 $87.71   7.671%   $94.4382   $94.44   $94.45   $94.40  
  Purchase #6 $99.76   8.812%   $108.5509   $108.55   $108.55   $108.60  
  Purchase #7 $202.77   11.596%   $226.2832   $226.28   $226.30   $226.30  
  7 purchase totals = $696.08       $757.9408   $757.94   $758.00   $757.90