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 $86.95   5.797%   $91.9905   $91.99   $92.00   $92.00  
  Purchase #2 $185.34   9.582%   $203.0993   $203.10   $203.10   $203.10  
  Purchase #3 $60.76   5.721%   $64.2361   $64.24   $64.25   $64.20  
  Purchase #4 $168.56   13.364%   $191.0864   $191.09   $191.10   $191.10  
  Purchase #5 $26.83   12.145%   $30.0885   $30.09   $30.10   $30.10  
  Purchase #6 $239.70   6.307%   $254.8179   $254.82   $254.80   $254.80  
  Purchase #7 $110.56   5.509%   $116.6508   $116.65   $116.65   $116.70  
  7 purchase totals = $878.70       $951.9695   $951.98   $952.00   $952.00