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 $187.83   8.183%   $203.2001   $203.20   $203.20   $203.20  
  Purchase #2 $221.32   6.272%   $235.2012   $235.20   $235.20   $235.20  
  Purchase #3 $59.55   3.742%   $61.7784   $61.78   $61.80   $61.80  
  Purchase #4 $92.82   6.500%   $98.8533   $98.85   $98.85   $98.90  
  Purchase #5 $120.54   7.250%   $129.2792   $129.28   $129.30   $129.30  
  Purchase #6 $215.61   9.113%   $235.2585   $235.26   $235.25   $235.30  
  Purchase #7 $178.32   4.382%   $186.134   $186.13   $186.15   $186.10  
  7 purchase totals = $1,075.99       $1,149.7047   $1,149.70   $1,149.75   $1,149.80