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 $41.77   10.214%   $46.0364   $46.04   $46.05   $46.00  
  Purchase #2 $96.65   4.664%   $101.1578   $101.16   $101.15   $101.20  
  Purchase #3 $183.58   11.689%   $205.0387   $205.04   $205.05   $205.00  
  Purchase #4 $185.37   4.414%   $193.5522   $193.55   $193.55   $193.60  
  Purchase #5 $67.84   8.298%   $73.4694   $73.47   $73.45   $73.50  
  Purchase #6 $212.48   10.600%   $235.0029   $235.00   $235.00   $235.00  
  Purchase #7 $210.89   10.870%   $233.8137   $233.81   $233.80   $233.80  
  7 purchase totals = $998.58       $1,088.0711   $1,088.07   $1,088.05   $1,088.10