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 $208.64   9.154%   $227.7389   $227.74   $227.75   $227.70  
  Purchase #2 $211.94   10.231%   $233.6236   $233.62   $233.60   $233.60  
  Purchase #3 $16.56   4.632%   $17.3271   $17.33   $17.35   $17.30  
  Purchase #4 $64.88   10.678%   $71.8079   $71.81   $71.80   $71.80  
  Purchase #5 $183.46   6.444%   $195.2822   $195.28   $195.30   $195.30  
  Purchase #6 $77.87   9.475%   $85.2482   $85.25   $85.25   $85.20  
  Purchase #7 $191.43   9.729%   $210.0542   $210.05   $210.05   $210.10  
  7 purchase totals = $954.78       $1,041.0821   $1,041.08   $1,041.10   $1,041.00