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 $43.67   5.432%   $46.0422   $46.04   $46.05   $46.00  
  Purchase #2 $80.77   11.679%   $90.2031   $90.20   $90.20   $90.20  
  Purchase #3 $194.44   12.579%   $218.8986   $218.90   $218.90   $218.90  
  Purchase #4 $102.80   12.313%   $115.4578   $115.46   $115.45   $115.50  
  Purchase #5 $248.50   5.691%   $262.6421   $262.64   $262.65   $262.60  
  Purchase #6 $86.85   10.822%   $96.2489   $96.25   $96.25   $96.20  
  Purchase #7 $83.55   4.283%   $87.1284   $87.13   $87.15   $87.10  
  7 purchase totals = $840.58       $916.6211   $916.62   $916.65   $916.50