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 $60.87   3.414%   $62.9481   $62.95   $62.95   $62.90  
  Purchase #2 $216.99   10.390%   $239.5353   $239.54   $239.55   $239.50  
  Purchase #3 $98.26   3.322%   $101.5242   $101.52   $101.50   $101.50  
  Purchase #4 $144.42   5.839%   $152.8527   $152.85   $152.85   $152.90  
  Purchase #5 $237.98   3.553%   $246.4354   $246.44   $246.45   $246.40  
  Purchase #6 $230.62   7.332%   $247.5291   $247.53   $247.55   $247.50  
  Purchase #7 $147.97   9.472%   $161.9857   $161.99   $162.00   $162.00  
  7 purchase totals = $1,137.11       $1,212.8105   $1,212.82   $1,212.85   $1,212.70