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 $86.38   6.809%   $92.2616   $92.26   $92.25   $92.30  
  Purchase #2 $245.34   4.686%   $256.8366   $256.84   $256.85   $256.80  
  Purchase #3 $63.92   6.300%   $67.947   $67.95   $67.95   $67.90  
  Purchase #4 $233.99   5.709%   $247.3485   $247.35   $247.35   $247.30  
  Purchase #5 $156.57   4.795%   $164.0775   $164.08   $164.10   $164.10  
  Purchase #6 $187.89   6.838%   $200.7379   $200.74   $200.75   $200.70  
  Purchase #7 $71.65   4.554%   $74.9129   $74.91   $74.90   $74.90  
  7 purchase totals = $1,045.74       $1,104.1220   $1,104.13   $1,104.15   $1,104.00