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 $59.31   7.268%   $63.6207   $63.62   $63.60   $63.60  
  Purchase #2 $157.47   10.606%   $174.1713   $174.17   $174.15   $174.20  
  Purchase #3 $243.89   10.328%   $269.079   $269.08   $269.10   $269.10  
  Purchase #4 $174.69   10.687%   $193.3591   $193.36   $193.35   $193.40  
  Purchase #5 $222.96   6.658%   $237.8047   $237.80   $237.80   $237.80  
  Purchase #6 $82.58   8.204%   $89.3549   $89.35   $89.35   $89.40  
  Purchase #7 $189.25   7.220%   $202.9139   $202.91   $202.90   $202.90  
  7 purchase totals = $1,130.15       $1,230.3036   $1,230.29   $1,230.25   $1,230.40