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 $62.27   5.866%   $65.9228   $65.92   $65.90   $65.90  
  Purchase #2 $105.29   9.333%   $115.1167   $115.12   $115.10   $115.10  
  Purchase #3 $155.34   3.203%   $160.3155   $160.32   $160.30   $160.30  
  Purchase #4 $213.85   9.679%   $234.5485   $234.55   $234.55   $234.50  
  Purchase #5 $33.50   11.717%   $37.4252   $37.43   $37.45   $37.40  
  Purchase #6 $169.88   6.793%   $181.4199   $181.42   $181.40   $181.40  
  Purchase #7 $155.96   4.757%   $163.379   $163.38   $163.40   $163.40  
  7 purchase totals = $896.09       $958.1276   $958.14   $958.10   $958.00