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 $61.83   5.678%   $65.3407   $65.34   $65.35   $65.30  
  Purchase #2 $26.44   6.837%   $28.2477   $28.25   $28.25   $28.20  
  Purchase #3 $235.40   4.134%   $245.1314   $245.13   $245.15   $245.10  
  Purchase #4 $191.72   10.320%   $211.5055   $211.51   $211.50   $211.50  
  Purchase #5 $171.68   5.234%   $180.6657   $180.67   $180.65   $180.70  
  Purchase #6 $245.26   4.248%   $255.6786   $255.68   $255.70   $255.70  
  Purchase #7 $217.93   10.183%   $240.1218   $240.12   $240.10   $240.10  
  7 purchase totals = $1,150.26       $1,226.6914   $1,226.70   $1,226.70   $1,226.60