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 $85.60   9.763%   $93.9571   $93.96   $93.95   $94.00  
  Purchase #2 $51.35   9.778%   $56.371   $56.37   $56.35   $56.40  
  Purchase #3 $207.32   3.662%   $214.9121   $214.91   $214.90   $214.90  
  Purchase #4 $107.95   4.815%   $113.1478   $113.15   $113.15   $113.10  
  Purchase #5 $200.80   10.834%   $222.5547   $222.55   $222.55   $222.60  
  Purchase #6 $88.30   8.806%   $96.0757   $96.08   $96.10   $96.10  
  Purchase #7 $225.43   9.700%   $247.2967   $247.30   $247.30   $247.30  
  7 purchase totals = $966.75       $1,044.3151   $1,044.32   $1,044.30   $1,044.40