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 $92.67   3.549%   $95.9589   $95.96   $95.95   $96.00  
  Purchase #2 $167.45   5.585%   $176.8021   $176.80   $176.80   $176.80  
  Purchase #3 $250.35   3.868%   $260.0335   $260.03   $260.05   $260.00  
  Purchase #4 $240.50   4.479%   $251.272   $251.27   $251.25   $251.30  
  Purchase #5 $115.25   7.321%   $123.6875   $123.69   $123.70   $123.70  
  Purchase #6 $201.43   5.419%   $212.3455   $212.35   $212.35   $212.30  
  Purchase #7 $186.30   5.547%   $196.6341   $196.63   $196.65   $196.60  
  7 purchase totals = $1,253.95       $1,316.7336   $1,316.73   $1,316.75   $1,316.70