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 $241.65   10.730%   $267.579   $267.58   $267.60   $267.60  
  Purchase #2 $207.53   8.425%   $225.0144   $225.01   $225.00   $225.00  
  Purchase #3 $13.48   9.771%   $14.7971   $14.80   $14.80   $14.80  
  Purchase #4 $112.96   8.355%   $122.3978   $122.40   $122.40   $122.40  
  Purchase #5 $46.33   10.647%   $51.2628   $51.26   $51.25   $51.30  
  Purchase #6 $172.69   13.740%   $196.4176   $196.42   $196.40   $196.40  
  Purchase #7 $16.69   8.504%   $18.1093   $18.11   $18.10   $18.10  
  7 purchase totals = $811.33       $895.5780   $895.58   $895.55   $895.60