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 $84.92   11.165%   $94.4013   $94.40   $94.40   $94.40  
  Purchase #2 $145.40   5.139%   $152.8721   $152.87   $152.85   $152.90  
  Purchase #3 $80.68   9.340%   $88.2155   $88.22   $88.20   $88.20  
  Purchase #4 $234.62   12.583%   $264.1422   $264.14   $264.15   $264.10  
  Purchase #5 $212.83   5.324%   $224.1611   $224.16   $224.15   $224.20  
  Purchase #6 $215.57   8.125%   $233.0851   $233.09   $233.10   $233.10  
  Purchase #7 $194.62   5.616%   $205.5499   $205.55   $205.55   $205.50  
  7 purchase totals = $1,168.64       $1,262.4272   $1,262.43   $1,262.40   $1,262.40