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 $111.81   12.608%   $125.907   $125.91   $125.90   $125.90  
  Purchase #2 $59.68   10.494%   $65.9428   $65.94   $65.95   $65.90  
  Purchase #3 $91.27   5.190%   $96.0069   $96.01   $96.00   $96.00  
  Purchase #4 $13.76   5.734%   $14.549   $14.55   $14.55   $14.50  
  Purchase #5 $126.46   7.236%   $135.6106   $135.61   $135.60   $135.60  
  Purchase #6 $177.72   8.764%   $193.2954   $193.30   $193.30   $193.30  
  Purchase #7 $83.66   9.560%   $91.6579   $91.66   $91.65   $91.70  
  7 purchase totals = $664.36       $722.9696   $722.98   $722.95   $722.90