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 $117.60   7.283%   $126.1648   $126.16   $126.15   $126.20  
  Purchase #2 $147.75   4.187%   $153.9363   $153.94   $153.95   $153.90  
  Purchase #3 $158.26   4.364%   $165.1665   $165.17   $165.15   $165.20  
  Purchase #4 $222.45   13.195%   $251.8023   $251.80   $251.80   $251.80  
  Purchase #5 $76.89   4.300%   $80.1963   $80.20   $80.20   $80.20  
  Purchase #6 $151.43   13.638%   $172.082   $172.08   $172.10   $172.10  
  Purchase #7 $242.99   3.356%   $251.1447   $251.14   $251.15   $251.10  
  7 purchase totals = $1,117.37       $1,200.4929   $1,200.49   $1,200.50   $1,200.50