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 $48.45   11.407%   $53.9767   $53.98   $54.00   $54.00  
  Purchase #2 $16.64   8.631%   $18.0762   $18.08   $18.10   $18.10  
  Purchase #3 $53.83   12.842%   $60.7428   $60.74   $60.75   $60.70  
  Purchase #4 $92.71   3.758%   $96.194   $96.19   $96.20   $96.20  
  Purchase #5 $213.71   4.393%   $223.0983   $223.10   $223.10   $223.10  
  Purchase #6 $47.46   7.337%   $50.9421   $50.94   $50.95   $50.90  
  Purchase #7 $246.41   6.633%   $262.7544   $262.75   $262.75   $262.80  
  7 purchase totals = $719.21       $765.7845   $765.78   $765.85   $765.80