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 $119.32   5.851%   $126.3014   $126.30   $126.30   $126.30  
  Purchase #2 $167.76   8.768%   $182.4692   $182.47   $182.45   $182.50  
  Purchase #3 $162.33   3.813%   $168.5196   $168.52   $168.50   $168.50  
  Purchase #4 $69.92   11.279%   $77.8063   $77.81   $77.80   $77.80  
  Purchase #5 $219.82   4.487%   $229.6833   $229.68   $229.70   $229.70  
  Purchase #6 $206.75   10.409%   $228.2706   $228.27   $228.25   $228.30  
  Purchase #7 $115.26   7.607%   $124.0278   $124.03   $124.05   $124.00  
  7 purchase totals = $1,061.16       $1,137.0782   $1,137.08   $1,137.05   $1,137.10