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 $88.59   8.343%   $95.9811   $95.98   $96.00   $96.00  
  Purchase #2 $32.81   7.587%   $35.2993   $35.30   $35.30   $35.30  
  Purchase #3 $199.56   13.347%   $226.1953   $226.20   $226.20   $226.20  
  Purchase #4 $119.54   6.803%   $127.6723   $127.67   $127.65   $127.70  
  Purchase #5 $8.37   5.370%   $8.8195   $8.82   $8.80   $8.80  
  Purchase #6 $232.82   4.636%   $243.6135   $243.61   $243.60   $243.60  
  Purchase #7 $124.69   4.501%   $130.3023   $130.30   $130.30   $130.30  
  7 purchase totals = $806.38       $867.8833   $867.88   $867.85   $867.90