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 $60.77   11.780%   $67.9287   $67.93   $67.95   $67.90  
  Purchase #2 $73.96   4.148%   $77.0279   $77.03   $77.05   $77.00  
  Purchase #3 $38.26   12.622%   $43.0892   $43.09   $43.10   $43.10  
  Purchase #4 $215.94   9.352%   $236.1347   $236.13   $236.15   $236.10  
  Purchase #5 $84.69   13.228%   $95.8928   $95.89   $95.90   $95.90  
  Purchase #6 $76.89   10.290%   $84.802   $84.80   $84.80   $84.80  
  Purchase #7 $60.31   11.283%   $67.1148   $67.11   $67.10   $67.10  
  7 purchase totals = $610.82       $671.9901   $671.98   $672.05   $671.90