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 $53.81   13.687%   $61.175   $61.18   $61.20   $61.20  
  Purchase #2 $200.46   7.189%   $214.8711   $214.87   $214.85   $214.90  
  Purchase #3 $223.53   10.707%   $247.4634   $247.46   $247.45   $247.50  
  Purchase #4 $201.44   12.231%   $226.0781   $226.08   $226.10   $226.10  
  Purchase #5 $67.46   12.485%   $75.8824   $75.88   $75.90   $75.90  
  Purchase #6 $223.79   4.623%   $234.1358   $234.14   $234.15   $234.10  
  Purchase #7 $30.65   5.842%   $32.4406   $32.44   $32.45   $32.40  
  7 purchase totals = $1,001.14       $1,092.0464   $1,092.05   $1,092.10   $1,092.10