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 $85.29   10.562%   $94.2983   $94.30   $94.30   $94.30  
  Purchase #2 $151.36   12.630%   $170.4768   $170.48   $170.50   $170.50  
  Purchase #3 $238.99   8.127%   $258.4127   $258.41   $258.40   $258.40  
  Purchase #4 $55.50   10.452%   $61.3009   $61.30   $61.30   $61.30  
  Purchase #5 $142.81   3.355%   $147.6013   $147.60   $147.60   $147.60  
  Purchase #6 $227.88   4.117%   $237.2618   $237.26   $237.25   $237.30  
  Purchase #7 $85.52   9.180%   $93.3707   $93.37   $93.35   $93.40  
  7 purchase totals = $987.35       $1,062.7225   $1,062.72   $1,062.70   $1,062.80