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 $49.81   7.650%   $53.6205   $53.62   $53.60   $53.60  
  Purchase #2 $160.50   9.808%   $176.2418   $176.24   $176.25   $176.20  
  Purchase #3 $113.90   3.571%   $117.9674   $117.97   $117.95   $118.00  
  Purchase #4 $234.45   5.551%   $247.4643   $247.46   $247.45   $247.50  
  Purchase #5 $120.68   3.464%   $124.8604   $124.86   $124.85   $124.90  
  Purchase #6 $231.61   7.593%   $249.1961   $249.20   $249.20   $249.20  
  Purchase #7 $230.75   3.283%   $238.3255   $238.33   $238.35   $238.30  
  7 purchase totals = $1,141.70       $1,207.6760   $1,207.68   $1,207.65   $1,207.70