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 $207.74   5.671%   $219.5209   $219.52   $219.50   $219.50  
  Purchase #2 $12.49   12.867%   $14.0971   $14.10   $14.10   $14.10  
  Purchase #3 $232.31   8.113%   $251.1573   $251.16   $251.15   $251.20  
  Purchase #4 $163.97   10.446%   $181.0983   $181.10   $181.10   $181.10  
  Purchase #5 $202.49   9.463%   $221.6516   $221.65   $221.65   $221.70  
  Purchase #6 $195.40   5.868%   $206.8661   $206.87   $206.85   $206.90  
  Purchase #7 $107.36   6.384%   $114.2139   $114.21   $114.20   $114.20  
  7 purchase totals = $1,121.76       $1,208.6052   $1,208.61   $1,208.55   $1,208.70