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 $57.30   11.424%   $63.846   $63.85   $63.85   $63.80  
  Purchase #2 $35.37   5.294%   $37.2425   $37.24   $37.25   $37.20  
  Purchase #3 $144.51   4.258%   $150.6632   $150.66   $150.65   $150.70  
  Purchase #4 $23.56   5.258%   $24.7988   $24.80   $24.80   $24.80  
  Purchase #5 $163.97   8.326%   $177.6221   $177.62   $177.60   $177.60  
  Purchase #6 $212.93   10.301%   $234.8639   $234.86   $234.85   $234.90  
  Purchase #7 $69.42   4.564%   $72.5883   $72.59   $72.60   $72.60  
  7 purchase totals = $707.06       $761.6248   $761.62   $761.60   $761.60