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 $60.71   11.384%   $67.6212   $67.62   $67.60   $67.60  
  Purchase #2 $160.25   12.662%   $180.5409   $180.54   $180.55   $180.50  
  Purchase #3 $232.47   8.471%   $252.1625   $252.16   $252.15   $252.20  
  Purchase #4 $232.53   10.603%   $257.1852   $257.19   $257.20   $257.20  
  Purchase #5 $93.27   6.201%   $99.0537   $99.05   $99.05   $99.10  
  Purchase #6 $78.96   13.474%   $89.5991   $89.60   $89.60   $89.60  
  Purchase #7 $216.28   5.356%   $227.864   $227.86   $227.85   $227.90  
  7 purchase totals = $1,074.47       $1,174.0266   $1,174.02   $1,174.00   $1,174.10