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 $88.43   6.354%   $94.0488   $94.05   $94.05   $94.00  
  Purchase #2 $101.57   6.183%   $107.8501   $107.85   $107.85   $107.90  
  Purchase #3 $215.84   7.189%   $231.3567   $231.36   $231.35   $231.40  
  Purchase #4 $154.98   6.603%   $165.2133   $165.21   $165.20   $165.20  
  Purchase #5 $69.78   6.708%   $74.4608   $74.46   $74.45   $74.50  
  Purchase #6 $146.25   3.354%   $151.1552   $151.16   $151.15   $151.20  
  Purchase #7 $166.70   13.266%   $188.8144   $188.81   $188.80   $188.80  
  7 purchase totals = $943.55       $1,012.8993   $1,012.90   $1,012.85   $1,013.00