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 $126.42   8.560%   $137.2416   $137.24   $137.25   $137.20  
  Purchase #2 $248.61   7.143%   $266.3682   $266.37   $266.35   $266.40  
  Purchase #3 $90.27   3.658%   $93.5721   $93.57   $93.55   $93.60  
  Purchase #4 $244.99   4.478%   $255.9607   $255.96   $255.95   $256.00  
  Purchase #5 $191.55   6.757%   $204.493   $204.49   $204.50   $204.50  
  Purchase #6 $140.83   6.691%   $150.2529   $150.25   $150.25   $150.30  
  Purchase #7 $181.31   3.235%   $187.1754   $187.18   $187.20   $187.20  
  7 purchase totals = $1,223.98       $1,295.0639   $1,295.06   $1,295.05   $1,295.20