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 $122.82   7.755%   $132.3447   $132.34   $132.35   $132.30  
  Purchase #2 $189.26   3.242%   $195.3958   $195.40   $195.40   $195.40  
  Purchase #3 $78.72   6.724%   $84.0131   $84.01   $84.00   $84.00  
  Purchase #4 $184.97   7.406%   $198.6689   $198.67   $198.65   $198.70  
  Purchase #5 $113.74   3.825%   $118.0906   $118.09   $118.10   $118.10  
  Purchase #6 $221.58   11.267%   $246.5454   $246.55   $246.55   $246.50  
  Purchase #7 $33.60   7.557%   $36.1392   $36.14   $36.15   $36.10  
  7 purchase totals = $944.69       $1,011.1977   $1,011.20   $1,011.20   $1,011.10