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 $114.99   9.228%   $125.6013   $125.60   $125.60   $125.60  
  Purchase #2 $42.84   13.246%   $48.5146   $48.51   $48.50   $48.50  
  Purchase #3 $59.83   13.639%   $67.9902   $67.99   $68.00   $68.00  
  Purchase #4 $186.91   9.463%   $204.5973   $204.60   $204.60   $204.60  
  Purchase #5 $207.73   7.498%   $223.3056   $223.31   $223.30   $223.30  
  Purchase #6 $58.98   8.741%   $64.1354   $64.14   $64.15   $64.10  
  Purchase #7 $35.83   8.809%   $38.9863   $38.99   $39.00   $39.00  
  7 purchase totals = $707.11       $773.1307   $773.14   $773.15   $773.10