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 $69.95   3.454%   $72.3661   $72.37   $72.35   $72.40  
  Purchase #2 $176.68   10.267%   $194.8197   $194.82   $194.80   $194.80  
  Purchase #3 $71.66   5.439%   $75.5576   $75.56   $75.55   $75.60  
  Purchase #4 $59.80   6.442%   $63.6523   $63.65   $63.65   $63.70  
  Purchase #5 $144.87   9.714%   $158.9427   $158.94   $158.95   $158.90  
  Purchase #6 $177.61   13.527%   $201.6353   $201.64   $201.65   $201.60  
  Purchase #7 $230.70   5.556%   $243.5177   $243.52   $243.50   $243.50  
  7 purchase totals = $931.27       $1,010.4914   $1,010.50   $1,010.45   $1,010.50