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 $167.91   5.295%   $176.8008   $176.80   $176.80   $176.80  
  Purchase #2 $95.48   8.437%   $103.5356   $103.54   $103.55   $103.50  
  Purchase #3 $162.33   8.748%   $176.5306   $176.53   $176.55   $176.50  
  Purchase #4 $209.33   6.193%   $222.2938   $222.29   $222.30   $222.30  
  Purchase #5 $20.83   10.218%   $22.9584   $22.96   $22.95   $23.00  
  Purchase #6 $200.72   5.446%   $211.6512   $211.65   $211.65   $211.70  
  Purchase #7 $227.50   8.590%   $247.0423   $247.04   $247.05   $247.00  
  7 purchase totals = $1,084.10       $1,160.8127   $1,160.81   $1,160.85   $1,160.80