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 $207.47   12.615%   $233.6423   $233.64   $233.65   $233.60  
  Purchase #2 $239.52   11.185%   $266.3103   $266.31   $266.30   $266.30  
  Purchase #3 $163.27   12.488%   $183.6592   $183.66   $183.65   $183.70  
  Purchase #4 $225.99   3.627%   $234.1867   $234.19   $234.20   $234.20  
  Purchase #5 $74.42   8.818%   $80.9824   $80.98   $81.00   $81.00  
  Purchase #6 $202.29   6.504%   $215.4469   $215.45   $215.45   $215.40  
  Purchase #7 $207.31   6.865%   $221.5418   $221.54   $221.55   $221.50  
  7 purchase totals = $1,320.27       $1,435.7696   $1,435.77   $1,435.80   $1,435.70