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 $60.95   13.200%   $68.9954   $69.00   $69.00   $69.00  
  Purchase #2 $108.74   4.220%   $113.3288   $113.33   $113.35   $113.30  
  Purchase #3 $218.88   10.366%   $241.5691   $241.57   $241.55   $241.60  
  Purchase #4 $199.66   9.868%   $219.3624   $219.36   $219.35   $219.40  
  Purchase #5 $13.70   13.287%   $15.5203   $15.52   $15.50   $15.50  
  Purchase #6 $64.93   8.394%   $70.3802   $70.38   $70.40   $70.40  
  Purchase #7 $62.66   8.767%   $68.1534   $68.15   $68.15   $68.20  
  7 purchase totals = $729.52       $797.3096   $797.31   $797.30   $797.40