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 $94.25   12.505%   $106.036   $106.04   $106.05   $106.00  
  Purchase #2 $162.49   13.329%   $184.1483   $184.15   $184.15   $184.10  
  Purchase #3 $172.41   8.535%   $187.1252   $187.13   $187.15   $187.10  
  Purchase #4 $206.97   3.642%   $214.5078   $214.51   $214.50   $214.50  
  Purchase #5 $80.34   13.471%   $91.1626   $91.16   $91.15   $91.20  
  Purchase #6 $201.91   8.671%   $219.4176   $219.42   $219.40   $219.40  
  Purchase #7 $234.39   5.501%   $247.2838   $247.28   $247.30   $247.30  
  7 purchase totals = $1,152.76       $1,249.6813   $1,249.69   $1,249.70   $1,249.60