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 $61.43   13.194%   $69.5351   $69.54   $69.55   $69.50  
  Purchase #2 $203.43   6.273%   $216.1912   $216.19   $216.20   $216.20  
  Purchase #3 $168.42   13.694%   $191.4834   $191.48   $191.50   $191.50  
  Purchase #4 $199.74   7.269%   $214.2591   $214.26   $214.25   $214.30  
  Purchase #5 $31.35   9.107%   $34.205   $34.21   $34.20   $34.20  
  Purchase #6 $71.49   13.819%   $81.3692   $81.37   $81.35   $81.40  
  Purchase #7 $76.62   13.479%   $86.9476   $86.95   $86.95   $86.90  
  7 purchase totals = $812.48       $893.9906   $894.00   $894.00   $894.00