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 $47.32   10.383%   $52.2332   $52.23   $52.25   $52.20  
  Purchase #2 $140.74   3.771%   $146.0473   $146.05   $146.05   $146.00  
  Purchase #3 $151.68   10.441%   $167.5169   $167.52   $167.50   $167.50  
  Purchase #4 $191.92   4.726%   $200.9901   $200.99   $201.00   $201.00  
  Purchase #5 $194.61   4.723%   $203.8014   $203.80   $203.80   $203.80  
  Purchase #6 $67.59   13.189%   $76.5044   $76.50   $76.50   $76.50  
  Purchase #7 $197.28   9.200%   $215.4298   $215.43   $215.45   $215.40  
  7 purchase totals = $991.14       $1,062.5231   $1,062.52   $1,062.55   $1,062.40