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 $208.98   8.406%   $226.5469   $226.55   $226.55   $226.50  
  Purchase #2 $36.82   4.263%   $38.3896   $38.39   $38.40   $38.40  
  Purchase #3 $98.44   11.463%   $109.7242   $109.72   $109.70   $109.70  
  Purchase #4 $173.90   9.382%   $190.2153   $190.22   $190.20   $190.20  
  Purchase #5 $204.62   5.631%   $216.1422   $216.14   $216.15   $216.10  
  Purchase #6 $234.85   5.472%   $247.701   $247.70   $247.70   $247.70  
  Purchase #7 $146.80   5.815%   $155.3364   $155.34   $155.35   $155.30  
  7 purchase totals = $1,104.41       $1,184.0556   $1,184.06   $1,184.05   $1,183.90