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 $85.36   13.537%   $96.9152   $96.92   $96.90   $96.90  
  Purchase #2 $202.79   11.592%   $226.2974   $226.30   $226.30   $226.30  
  Purchase #3 $65.65   13.156%   $74.2869   $74.29   $74.30   $74.30  
  Purchase #4 $61.97   7.292%   $66.4889   $66.49   $66.50   $66.50  
  Purchase #5 $232.73   11.321%   $259.0774   $259.08   $259.10   $259.10  
  Purchase #6 $215.73   5.308%   $227.1809   $227.18   $227.20   $227.20  
  Purchase #7 $196.89   9.828%   $216.2403   $216.24   $216.25   $216.20  
  7 purchase totals = $1,061.12       $1,166.4870   $1,166.50   $1,166.55   $1,166.50