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 $158.46   11.486%   $176.6607   $176.66   $176.65   $176.70  
  Purchase #2 $215.98   5.401%   $227.6451   $227.65   $227.65   $227.60  
  Purchase #3 $87.43   5.264%   $92.0323   $92.03   $92.05   $92.00  
  Purchase #4 $32.97   3.419%   $34.0972   $34.10   $34.10   $34.10  
  Purchase #5 $93.74   13.680%   $106.5636   $106.56   $106.55   $106.60  
  Purchase #6 $65.32   4.715%   $68.3998   $68.40   $68.40   $68.40  
  Purchase #7 $62.91   7.203%   $67.4414   $67.44   $67.45   $67.40  
  7 purchase totals = $716.81       $772.8401   $772.84   $772.85   $772.80