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 $126.25   11.837%   $141.1942   $141.19   $141.20   $141.20  
  Purchase #2 $177.80   4.474%   $185.7548   $185.75   $185.75   $185.80  
  Purchase #3 $97.77   3.631%   $101.32   $101.32   $101.30   $101.30  
  Purchase #4 $210.53   4.453%   $219.9049   $219.90   $219.90   $219.90  
  Purchase #5 $9.35   13.843%   $10.6443   $10.64   $10.65   $10.60  
  Purchase #6 $233.62   6.387%   $248.5413   $248.54   $248.55   $248.50  
  Purchase #7 $142.88   8.609%   $155.1805   $155.18   $155.20   $155.20  
  7 purchase totals = $998.20       $1,062.5400   $1,062.52   $1,062.55   $1,062.50