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 $216.28   8.638%   $234.9623   $234.96   $234.95   $235.00  
  Purchase #2 $244.81   9.252%   $267.4598   $267.46   $267.45   $267.50  
  Purchase #3 $43.41   10.223%   $47.8478   $47.85   $47.85   $47.80  
  Purchase #4 $13.46   8.661%   $14.6258   $14.63   $14.65   $14.60  
  Purchase #5 $208.92   5.735%   $220.9016   $220.90   $220.90   $220.90  
  Purchase #6 $91.61   5.498%   $96.6467   $96.65   $96.65   $96.60  
  Purchase #7 $115.86   13.506%   $131.5081   $131.51   $131.50   $131.50  
  7 purchase totals = $934.35       $1,013.9521   $1,013.96   $1,013.95   $1,013.90