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 $174.57   5.462%   $184.105   $184.11   $184.10   $184.10  
  Purchase #2 $135.52   5.516%   $142.9953   $143.00   $143.00   $143.00  
  Purchase #3 $12.34   10.308%   $13.612   $13.61   $13.60   $13.60  
  Purchase #4 $135.56   11.455%   $151.0884   $151.09   $151.10   $151.10  
  Purchase #5 $187.54   4.115%   $195.2573   $195.26   $195.25   $195.30  
  Purchase #6 $190.76   7.577%   $205.2139   $205.21   $205.20   $205.20  
  Purchase #7 $159.33   5.553%   $168.1776   $168.18   $168.20   $168.20  
  7 purchase totals = $995.62       $1,060.4495   $1,060.46   $1,060.45   $1,060.50