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 $53.54   9.636%   $58.6991   $58.70   $58.70   $58.70  
  Purchase #2 $59.61   6.597%   $63.5425   $63.54   $63.55   $63.50  
  Purchase #3 $91.69   5.457%   $96.6935   $96.69   $96.70   $96.70  
  Purchase #4 $107.74   6.816%   $115.0836   $115.08   $115.10   $115.10  
  Purchase #5 $206.96   3.261%   $213.709   $213.71   $213.70   $213.70  
  Purchase #6 $225.37   4.771%   $236.1224   $236.12   $236.10   $236.10  
  Purchase #7 $76.75   6.818%   $81.9828   $81.98   $82.00   $82.00  
  7 purchase totals = $821.66       $865.8329   $865.82   $865.85   $865.80