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 $216.59   12.481%   $243.6226   $243.62   $243.60   $243.60  
  Purchase #2 $192.85   6.843%   $206.0467   $206.05   $206.05   $206.00  
  Purchase #3 $219.52   5.350%   $231.2643   $231.26   $231.25   $231.30  
  Purchase #4 $224.82   12.624%   $253.2013   $253.20   $253.20   $253.20  
  Purchase #5 $226.55   5.653%   $239.3569   $239.36   $239.35   $239.40  
  Purchase #6 $204.43   8.246%   $221.2873   $221.29   $221.30   $221.30  
  Purchase #7 $63.30   7.279%   $67.9076   $67.91   $67.90   $67.90  
  7 purchase totals = $1,348.06       $1,462.6867   $1,462.69   $1,462.65   $1,462.70