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 $44.25   10.806%   $49.0317   $49.03   $49.05   $49.00  
  Purchase #2 $112.45   10.846%   $124.6463   $124.65   $124.65   $124.60  
  Purchase #3 $179.81   8.734%   $195.5146   $195.51   $195.50   $195.50  
  Purchase #4 $124.69   3.398%   $128.927   $128.93   $128.95   $128.90  
  Purchase #5 $172.52   12.513%   $194.1074   $194.11   $194.10   $194.10  
  Purchase #6 $246.77   6.260%   $262.2178   $262.22   $262.20   $262.20  
  Purchase #7 $90.98   6.725%   $97.0984   $97.10   $97.10   $97.10  
  7 purchase totals = $971.47       $1,051.5432   $1,051.55   $1,051.55   $1,051.40