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 $241.67   11.323%   $269.0343   $269.03   $269.05   $269.00  
  Purchase #2 $103.98   11.276%   $115.7048   $115.70   $115.70   $115.70  
  Purchase #3 $154.58   3.220%   $159.5575   $159.56   $159.55   $159.60  
  Purchase #4 $181.30   9.655%   $198.8045   $198.80   $198.80   $198.80  
  Purchase #5 $208.48   3.691%   $216.175   $216.18   $216.20   $216.20  
  Purchase #6 $131.78   8.665%   $143.1987   $143.20   $143.20   $143.20  
  Purchase #7 $19.40   5.630%   $20.4922   $20.49   $20.50   $20.50  
  7 purchase totals = $1,041.19       $1,122.9670   $1,122.96   $1,123.00   $1,123.00