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 $194.91   10.801%   $215.9622   $215.96   $215.95   $216.00  
  Purchase #2 $246.47   6.764%   $263.1412   $263.14   $263.15   $263.10  
  Purchase #3 $11.61   7.601%   $12.4925   $12.49   $12.50   $12.50  
  Purchase #4 $160.45   11.858%   $179.4762   $179.48   $179.50   $179.50  
  Purchase #5 $71.95   12.597%   $81.0135   $81.01   $81.00   $81.00  
  Purchase #6 $203.63   10.325%   $224.6548   $224.65   $224.65   $224.70  
  Purchase #7 $78.93   11.707%   $88.1703   $88.17   $88.15   $88.20  
  7 purchase totals = $967.95       $1,064.9107   $1,064.90   $1,064.90   $1,065.00