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 $85.75   11.840%   $95.9028   $95.90   $95.90   $95.90  
  Purchase #2 $148.36   12.615%   $167.0756   $167.08   $167.10   $167.10  
  Purchase #3 $73.61   12.392%   $82.7318   $82.73   $82.75   $82.70  
  Purchase #4 $198.57   8.345%   $215.1407   $215.14   $215.15   $215.10  
  Purchase #5 $198.30   13.137%   $224.3507   $224.35   $224.35   $224.40  
  Purchase #6 $31.97   9.441%   $34.9883   $34.99   $35.00   $35.00  
  Purchase #7 $60.68   12.182%   $68.072   $68.07   $68.05   $68.10  
  7 purchase totals = $797.24       $888.2619   $888.26   $888.30   $888.30