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 $61.38   13.421%   $69.6178   $69.62   $69.60   $69.60  
  Purchase #2 $58.53   6.415%   $62.2847   $62.28   $62.30   $62.30  
  Purchase #3 $61.99   7.811%   $66.832   $66.83   $66.85   $66.80  
  Purchase #4 $77.77   13.320%   $88.129   $88.13   $88.15   $88.10  
  Purchase #5 $45.95   3.547%   $47.5798   $47.58   $47.60   $47.60  
  Purchase #6 $86.30   11.790%   $96.4748   $96.47   $96.45   $96.50  
  Purchase #7 $11.26   6.656%   $12.0095   $12.01   $12.00   $12.00  
  7 purchase totals = $403.18       $442.9276   $442.92   $442.95   $442.90