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 $160.76   13.687%   $182.7632   $182.76   $182.75   $182.80  
  Purchase #2 $97.90   5.263%   $103.0525   $103.05   $103.05   $103.10  
  Purchase #3 $239.90   9.430%   $262.5226   $262.52   $262.50   $262.50  
  Purchase #4 $200.58   6.520%   $213.6578   $213.66   $213.65   $213.70  
  Purchase #5 $144.84   12.607%   $163.1   $163.10   $163.10   $163.10  
  Purchase #6 $33.27   10.592%   $36.794   $36.79   $36.80   $36.80  
  Purchase #7 $156.30   8.427%   $169.4714   $169.47   $169.45   $169.50  
  7 purchase totals = $1,033.55       $1,131.3615   $1,131.35   $1,131.30   $1,131.50