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 $214.86   8.282%   $232.6547   $232.65   $232.65   $232.70  
  Purchase #2 $232.43   11.399%   $258.9247   $258.92   $258.90   $258.90  
  Purchase #3 $78.34   4.670%   $81.9985   $82.00   $82.00   $82.00  
  Purchase #4 $102.98   3.321%   $106.4   $106.40   $106.40   $106.40  
  Purchase #5 $99.68   6.619%   $106.2778   $106.28   $106.30   $106.30  
  Purchase #6 $68.96   6.588%   $73.5031   $73.50   $73.50   $73.50  
  Purchase #7 $225.43   11.748%   $251.9135   $251.91   $251.90   $251.90  
  7 purchase totals = $1,022.68       $1,111.6723   $1,111.66   $1,111.65   $1,111.70