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 $59.66   4.413%   $62.2928   $62.29   $62.30   $62.30  
  Purchase #2 $217.53   13.617%   $247.1511   $247.15   $247.15   $247.20  
  Purchase #3 $86.63   8.469%   $93.9667   $93.97   $93.95   $94.00  
  Purchase #4 $44.82   5.409%   $47.2443   $47.24   $47.25   $47.20  
  Purchase #5 $150.25   11.450%   $167.4536   $167.45   $167.45   $167.50  
  Purchase #6 $187.36   13.437%   $212.5356   $212.54   $212.55   $212.50  
  Purchase #7 $23.52   12.438%   $26.4454   $26.45   $26.45   $26.40  
  7 purchase totals = $769.77       $857.0895   $857.09   $857.10   $857.10