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 $60.32   13.740%   $68.608   $68.61   $68.60   $68.60  
  Purchase #2 $176.63   5.858%   $186.977   $186.98   $187.00   $187.00  
  Purchase #3 $21.96   9.222%   $23.9852   $23.99   $24.00   $24.00  
  Purchase #4 $32.63   4.560%   $34.1179   $34.12   $34.10   $34.10  
  Purchase #5 $155.27   3.202%   $160.2417   $160.24   $160.25   $160.20  
  Purchase #6 $202.99   3.244%   $209.575   $209.58   $209.60   $209.60  
  Purchase #7 $222.35   7.754%   $239.591   $239.59   $239.60   $239.60  
  7 purchase totals = $872.15       $923.0958   $923.11   $923.15   $923.10