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 $116.63   9.769%   $128.0236   $128.02   $128.00   $128.00  
  Purchase #2 $60.75   13.746%   $69.1007   $69.10   $69.10   $69.10  
  Purchase #3 $96.73   9.184%   $105.6137   $105.61   $105.60   $105.60  
  Purchase #4 $188.32   3.811%   $195.4969   $195.50   $195.50   $195.50  
  Purchase #5 $171.88   7.506%   $184.7813   $184.78   $184.80   $184.80  
  Purchase #6 $239.70   11.263%   $266.6974   $266.70   $266.70   $266.70  
  Purchase #7 $149.93   11.369%   $166.9755   $166.98   $167.00   $167.00  
  7 purchase totals = $1,023.94       $1,116.6891   $1,116.69   $1,116.70   $1,116.70