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 $106.87   8.763%   $116.235   $116.24   $116.25   $116.20  
  Purchase #2 $171.65   6.400%   $182.6356   $182.64   $182.65   $182.60  
  Purchase #3 $155.52   5.390%   $163.9025   $163.90   $163.90   $163.90  
  Purchase #4 $231.87   7.596%   $249.4828   $249.48   $249.50   $249.50  
  Purchase #5 $166.75   5.612%   $176.108   $176.11   $176.10   $176.10  
  Purchase #6 $98.70   13.269%   $111.7965   $111.80   $111.80   $111.80  
  Purchase #7 $181.84   11.499%   $202.7498   $202.75   $202.75   $202.70  
  7 purchase totals = $1,113.20       $1,202.9102   $1,202.92   $1,202.95   $1,202.80