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 $87.37   7.597%   $94.0075   $94.01   $94.00   $94.00  
  Purchase #2 $211.57   10.836%   $234.4957   $234.50   $234.50   $234.50  
  Purchase #3 $93.61   9.342%   $102.355   $102.36   $102.35   $102.40  
  Purchase #4 $24.86   3.280%   $25.6754   $25.68   $25.70   $25.70  
  Purchase #5 $178.29   8.521%   $193.4821   $193.48   $193.50   $193.50  
  Purchase #6 $206.80   3.617%   $214.28   $214.28   $214.30   $214.30  
  Purchase #7 $61.99   11.220%   $68.9453   $68.95   $68.95   $68.90  
  7 purchase totals = $864.49       $933.2410   $933.26   $933.30   $933.30