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 $98.29   7.874%   $106.0294   $106.03   $106.05   $106.00  
  Purchase #2 $55.79   4.537%   $58.3212   $58.32   $58.30   $58.30  
  Purchase #3 $177.97   5.575%   $187.8918   $187.89   $187.90   $187.90  
  Purchase #4 $119.81   11.644%   $133.7607   $133.76   $133.75   $133.80  
  Purchase #5 $193.95   10.171%   $213.6767   $213.68   $213.70   $213.70  
  Purchase #6 $160.38   4.450%   $167.5169   $167.52   $167.50   $167.50  
  Purchase #7 $91.73   6.570%   $97.7567   $97.76   $97.75   $97.80  
  7 purchase totals = $897.92       $964.9534   $964.96   $964.95   $965.00