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 $225.69   4.797%   $236.5163   $236.52   $236.50   $236.50  
  Purchase #2 $41.64   8.666%   $45.2485   $45.25   $45.25   $45.20  
  Purchase #3 $232.82   3.202%   $240.2749   $240.27   $240.25   $240.30  
  Purchase #4 $47.33   12.584%   $53.286   $53.29   $53.30   $53.30  
  Purchase #5 $147.41   6.107%   $156.4123   $156.41   $156.40   $156.40  
  Purchase #6 $156.63   3.427%   $161.9977   $162.00   $162.00   $162.00  
  Purchase #7 $156.99   7.196%   $168.287   $168.29   $168.30   $168.30  
  7 purchase totals = $1,008.51       $1,062.0227   $1,062.03   $1,062.00   $1,062.00