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 $56.59   9.755%   $62.1104   $62.11   $62.10   $62.10  
  Purchase #2 $42.92   7.165%   $45.9952   $46.00   $46.00   $46.00  
  Purchase #3 $138.33   12.419%   $155.5092   $155.51   $155.50   $155.50  
  Purchase #4 $180.60   3.791%   $187.4465   $187.45   $187.45   $187.40  
  Purchase #5 $23.81   4.743%   $24.9393   $24.94   $24.95   $24.90  
  Purchase #6 $107.66   8.865%   $117.2041   $117.20   $117.20   $117.20  
  Purchase #7 $129.44   11.436%   $144.2428   $144.24   $144.25   $144.20  
  7 purchase totals = $679.35       $737.4475   $737.45   $737.45   $737.30