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 $209.68   3.263%   $216.5219   $216.52   $216.50   $216.50  
  Purchase #2 $38.76   9.121%   $42.2953   $42.30   $42.30   $42.30  
  Purchase #3 $72.83   10.640%   $80.5791   $80.58   $80.60   $80.60  
  Purchase #4 $169.25   3.601%   $175.3447   $175.34   $175.35   $175.30  
  Purchase #5 $244.27   5.593%   $257.932   $257.93   $257.95   $257.90  
  Purchase #6 $161.29   6.811%   $172.2755   $172.28   $172.30   $172.30  
  Purchase #7 $240.84   9.251%   $263.1201   $263.12   $263.10   $263.10  
  7 purchase totals = $1,136.92       $1,208.0686   $1,208.07   $1,208.10   $1,208.00