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 $70.95   4.517%   $74.1548   $74.15   $74.15   $74.20  
  Purchase #2 $152.29   3.124%   $157.0475   $157.05   $157.05   $157.00  
  Purchase #3 $238.44   10.595%   $263.7027   $263.70   $263.70   $263.70  
  Purchase #4 $79.72   10.441%   $88.0436   $88.04   $88.05   $88.00  
  Purchase #5 $81.94   6.127%   $86.9605   $86.96   $86.95   $87.00  
  Purchase #6 $200.75   6.807%   $214.4151   $214.42   $214.40   $214.40  
  Purchase #7 $137.34   6.308%   $146.0034   $146.00   $146.00   $146.00  
  7 purchase totals = $961.43       $1,030.3276   $1,030.32   $1,030.30   $1,030.30