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 $64.67   13.546%   $73.4302   $73.43   $73.45   $73.40  
  Purchase #2 $204.27   4.861%   $214.1996   $214.20   $214.20   $214.20  
  Purchase #3 $83.32   4.383%   $86.9719   $86.97   $86.95   $87.00  
  Purchase #4 $216.69   11.243%   $241.0525   $241.05   $241.05   $241.10  
  Purchase #5 $33.43   10.486%   $36.9355   $36.94   $36.95   $36.90  
  Purchase #6 $186.84   7.432%   $200.7259   $200.73   $200.75   $200.70  
  Purchase #7 $8.98   5.758%   $9.4971   $9.50   $9.50   $9.50  
  7 purchase totals = $798.20       $862.8127   $862.82   $862.85   $862.80