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 $62.84   9.758%   $68.9719   $68.97   $68.95   $69.00  
  Purchase #2 $125.44   12.439%   $141.0435   $141.04   $141.05   $141.00  
  Purchase #3 $31.76   4.260%   $33.113   $33.11   $33.10   $33.10  
  Purchase #4 $229.26   8.185%   $248.0249   $248.02   $248.00   $248.00  
  Purchase #5 $175.85   5.372%   $185.2967   $185.30   $185.30   $185.30  
  Purchase #6 $27.79   3.457%   $28.7507   $28.75   $28.75   $28.80  
  Purchase #7 $47.46   5.277%   $49.9645   $49.96   $49.95   $50.00  
  7 purchase totals = $700.40       $755.1652   $755.15   $755.10   $755.20