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 $219.77   8.124%   $237.6241   $237.62   $237.60   $237.60  
  Purchase #2 $104.52   13.596%   $118.7305   $118.73   $118.75   $118.70  
  Purchase #3 $26.82   9.804%   $29.4494   $29.45   $29.45   $29.40  
  Purchase #4 $54.80   12.581%   $61.6944   $61.69   $61.70   $61.70  
  Purchase #5 $52.59   6.526%   $56.022   $56.02   $56.00   $56.00  
  Purchase #6 $101.90   11.423%   $113.54   $113.54   $113.55   $113.50  
  Purchase #7 $112.46   6.832%   $120.1433   $120.14   $120.15   $120.10  
  7 purchase totals = $672.86       $737.2037   $737.19   $737.20   $737.00