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 $12.95   11.664%   $14.4605   $14.46   $14.45   $14.50  
  Purchase #2 $5.95   6.399%   $6.3307   $6.33   $6.35   $6.30  
  Purchase #3 $88.94   8.656%   $96.6386   $96.64   $96.65   $96.60  
  Purchase #4 $59.50   8.555%   $64.5902   $64.59   $64.60   $64.60  
  Purchase #5 $64.52   6.591%   $68.7725   $68.77   $68.75   $68.80  
  Purchase #6 $91.81   12.451%   $103.2413   $103.24   $103.25   $103.20  
  Purchase #7 $95.25   11.469%   $106.1742   $106.17   $106.15   $106.20  
  7 purchase totals = $418.92       $460.2080   $460.20   $460.20   $460.20