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 $84.70   12.350%   $95.1605   $95.16   $95.15   $95.20  
  Purchase #2 $194.78   3.374%   $201.3519   $201.35   $201.35   $201.40  
  Purchase #3 $108.72   8.125%   $117.5535   $117.55   $117.55   $117.60  
  Purchase #4 $128.35   3.546%   $132.9013   $132.90   $132.90   $132.90  
  Purchase #5 $79.90   4.115%   $83.1879   $83.19   $83.20   $83.20  
  Purchase #6 $187.28   4.478%   $195.6664   $195.67   $195.65   $195.70  
  Purchase #7 $240.50   7.781%   $259.2133   $259.21   $259.20   $259.20  
  7 purchase totals = $1,024.23       $1,085.0348   $1,085.03   $1,085.00   $1,085.20