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 $182.68   6.341%   $194.2637   $194.26   $194.25   $194.30  
  Purchase #2 $67.93   7.657%   $73.1314   $73.13   $73.15   $73.10  
  Purchase #3 $182.46   6.834%   $194.9293   $194.93   $194.95   $194.90  
  Purchase #4 $201.74   4.430%   $210.6771   $210.68   $210.70   $210.70  
  Purchase #5 $115.98   13.724%   $131.8971   $131.90   $131.90   $131.90  
  Purchase #6 $144.30   3.640%   $149.5525   $149.55   $149.55   $149.60  
  Purchase #7 $68.64   4.479%   $71.7144   $71.71   $71.70   $71.70  
  7 purchase totals = $963.73       $1,026.1655   $1,026.16   $1,026.20   $1,026.20