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 $54.75   13.568%   $62.1785   $62.18   $62.20   $62.20  
  Purchase #2 $195.32   6.386%   $207.7931   $207.79   $207.80   $207.80  
  Purchase #3 $215.92   13.793%   $245.7018   $245.70   $245.70   $245.70  
  Purchase #4 $71.66   6.661%   $76.4333   $76.43   $76.45   $76.40  
  Purchase #5 $168.95   8.530%   $183.3614   $183.36   $183.35   $183.40  
  Purchase #6 $42.84   8.203%   $46.3542   $46.35   $46.35   $46.40  
  Purchase #7 $202.91   6.333%   $215.7603   $215.76   $215.75   $215.80  
  7 purchase totals = $952.35       $1,037.5826   $1,037.57   $1,037.60   $1,037.70