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 $57.58   3.560%   $59.6298   $59.63   $59.65   $59.60  
  Purchase #2 $236.43   6.536%   $251.8831   $251.88   $251.90   $251.90  
  Purchase #3 $82.64   12.471%   $92.946   $92.95   $92.95   $92.90  
  Purchase #4 $172.84   9.870%   $189.8993   $189.90   $189.90   $189.90  
  Purchase #5 $188.43   4.562%   $197.0262   $197.03   $197.05   $197.00  
  Purchase #6 $56.61   7.210%   $60.6916   $60.69   $60.70   $60.70  
  Purchase #7 $137.41   13.666%   $156.1885   $156.19   $156.20   $156.20  
  7 purchase totals = $931.94       $1,008.2645   $1,008.27   $1,008.35   $1,008.20