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 $96.69   8.669%   $105.0721   $105.07   $105.05   $105.10  
  Purchase #2 $208.52   12.224%   $234.0095   $234.01   $234.00   $234.00  
  Purchase #3 $111.27   8.133%   $120.3196   $120.32   $120.30   $120.30  
  Purchase #4 $122.29   3.655%   $126.7597   $126.76   $126.75   $126.80  
  Purchase #5 $226.35   6.503%   $241.0695   $241.07   $241.05   $241.10  
  Purchase #6 $75.61   12.805%   $85.2919   $85.29   $85.30   $85.30  
  Purchase #7 $65.64   11.298%   $73.056   $73.06   $73.05   $73.10  
  7 purchase totals = $906.37       $985.5783   $985.58   $985.50   $985.70