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 $167.73   8.326%   $181.6952   $181.70   $181.70   $181.70  
  Purchase #2 $233.85   7.796%   $252.0809   $252.08   $252.10   $252.10  
  Purchase #3 $221.90   7.614%   $238.7955   $238.80   $238.80   $238.80  
  Purchase #4 $61.38   9.358%   $67.1239   $67.12   $67.10   $67.10  
  Purchase #5 $107.79   9.351%   $117.8694   $117.87   $117.85   $117.90  
  Purchase #6 $107.78   10.406%   $118.9956   $119.00   $119.00   $119.00  
  Purchase #7 $54.66   3.417%   $56.5277   $56.53   $56.55   $56.50  
  7 purchase totals = $955.09       $1,033.0882   $1,033.10   $1,033.10   $1,033.10