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 $91.68   4.303%   $95.625   $95.63   $95.65   $95.60  
  Purchase #2 $162.27   5.210%   $170.7243   $170.72   $170.70   $170.70  
  Purchase #3 $85.90   10.139%   $94.6094   $94.61   $94.60   $94.60  
  Purchase #4 $238.45   4.128%   $248.2932   $248.29   $248.30   $248.30  
  Purchase #5 $168.85   9.147%   $184.2947   $184.29   $184.30   $184.30  
  Purchase #6 $37.80   6.450%   $40.2381   $40.24   $40.25   $40.20  
  Purchase #7 $28.63   12.541%   $32.2205   $32.22   $32.20   $32.20  
  7 purchase totals = $813.58       $866.0052   $866.00   $866.00   $865.90