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 $212.29   9.270%   $231.9693   $231.97   $231.95   $232.00  
  Purchase #2 $81.43   4.494%   $85.0895   $85.09   $85.10   $85.10  
  Purchase #3 $26.72   10.831%   $29.614   $29.61   $29.60   $29.60  
  Purchase #4 $138.63   8.174%   $149.9616   $149.96   $149.95   $150.00  
  Purchase #5 $242.82   12.424%   $272.988   $272.99   $273.00   $273.00  
  Purchase #6 $153.42   7.383%   $164.747   $164.75   $164.75   $164.70  
  Purchase #7 $192.88   8.249%   $208.7907   $208.79   $208.80   $208.80  
  7 purchase totals = $1,048.19       $1,143.1601   $1,143.16   $1,143.15   $1,143.20