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 $43.99   4.590%   $46.0091   $46.01   $46.00   $46.00  
  Purchase #2 $160.83   12.803%   $181.4211   $181.42   $181.40   $181.40  
  Purchase #3 $227.53   9.275%   $248.6334   $248.63   $248.65   $248.60  
  Purchase #4 $84.58   9.435%   $92.5601   $92.56   $92.55   $92.60  
  Purchase #5 $116.81   13.474%   $132.549   $132.55   $132.55   $132.50  
  Purchase #6 $206.52   10.394%   $227.9857   $227.99   $228.00   $228.00  
  Purchase #7 $26.42   5.704%   $27.927   $27.93   $27.95   $27.90  
  7 purchase totals = $866.68       $957.0854   $957.09   $957.10   $957.00