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 $201.84   8.505%   $219.0065   $219.01   $219.00   $219.00  
  Purchase #2 $236.78   9.821%   $260.0342   $260.03   $260.05   $260.00  
  Purchase #3 $7.93   6.770%   $8.4669   $8.47   $8.45   $8.50  
  Purchase #4 $159.41   10.716%   $176.4924   $176.49   $176.50   $176.50  
  Purchase #5 $226.55   8.390%   $245.5575   $245.56   $245.55   $245.60  
  Purchase #6 $88.96   13.321%   $100.8104   $100.81   $100.80   $100.80  
  Purchase #7 $91.59   4.830%   $96.0138   $96.01   $96.00   $96.00  
  7 purchase totals = $1,013.06       $1,106.3817   $1,106.38   $1,106.35   $1,106.40