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 $85.28   12.593%   $96.0193   $96.02   $96.00   $96.00  
  Purchase #2 $106.63   5.153%   $112.1246   $112.12   $112.10   $112.10  
  Purchase #3 $131.83   7.139%   $141.2413   $141.24   $141.25   $141.20  
  Purchase #4 $19.77   11.649%   $22.073   $22.07   $22.05   $22.10  
  Purchase #5 $206.90   10.855%   $229.359   $229.36   $229.35   $229.40  
  Purchase #6 $245.33   12.535%   $276.0821   $276.08   $276.10   $276.10  
  Purchase #7 $196.98   7.638%   $212.0253   $212.03   $212.05   $212.00  
  7 purchase totals = $992.72       $1,088.9246   $1,088.92   $1,088.90   $1,088.90