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 $214.89   9.127%   $234.503   $234.50   $234.50   $234.50  
  Purchase #2 $95.40   11.362%   $106.2393   $106.24   $106.25   $106.20  
  Purchase #3 $11.29   7.350%   $12.1198   $12.12   $12.10   $12.10  
  Purchase #4 $73.46   8.264%   $79.5307   $79.53   $79.55   $79.50  
  Purchase #5 $92.40   3.666%   $95.7874   $95.79   $95.80   $95.80  
  Purchase #6 $40.57   11.540%   $45.2518   $45.25   $45.25   $45.30  
  Purchase #7 $180.31   12.265%   $202.425   $202.43   $202.45   $202.40  
  7 purchase totals = $708.32       $775.8570   $775.86   $775.90   $775.80