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 $44.43   4.508%   $46.4329   $46.43   $46.45   $46.40  
  Purchase #2 $191.36   9.562%   $209.6578   $209.66   $209.65   $209.70  
  Purchase #3 $71.54   8.491%   $77.6145   $77.61   $77.60   $77.60  
  Purchase #4 $114.64   6.722%   $122.3461   $122.35   $122.35   $122.30  
  Purchase #5 $42.91   11.541%   $47.8622   $47.86   $47.85   $47.90  
  Purchase #6 $82.96   6.454%   $88.3142   $88.31   $88.30   $88.30  
  Purchase #7 $211.44   5.526%   $223.1242   $223.12   $223.10   $223.10  
  7 purchase totals = $759.28       $815.3519   $815.34   $815.30   $815.30