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 $32.61   5.865%   $34.5226   $34.52   $34.50   $34.50  
  Purchase #2 $183.45   11.698%   $204.91   $204.91   $204.90   $204.90  
  Purchase #3 $241.78   6.359%   $257.1548   $257.15   $257.15   $257.20  
  Purchase #4 $244.69   11.792%   $273.5438   $273.54   $273.55   $273.50  
  Purchase #5 $126.51   3.367%   $130.7696   $130.77   $130.75   $130.80  
  Purchase #6 $33.28   6.482%   $35.4372   $35.44   $35.45   $35.40  
  Purchase #7 $230.34   3.191%   $237.6901   $237.69   $237.70   $237.70  
  7 purchase totals = $1,092.66       $1,174.0281   $1,174.02   $1,174.00   $1,174.00