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 $77.74   5.755%   $82.2139   $82.21   $82.20   $82.20  
  Purchase #2 $244.55   10.242%   $269.5968   $269.60   $269.60   $269.60  
  Purchase #3 $220.41   7.813%   $237.6306   $237.63   $237.65   $237.60  
  Purchase #4 $75.31   9.262%   $82.2852   $82.29   $82.30   $82.30  
  Purchase #5 $25.69   4.753%   $26.911   $26.91   $26.90   $26.90  
  Purchase #6 $198.61   10.231%   $218.9298   $218.93   $218.95   $218.90  
  Purchase #7 $232.70   10.496%   $257.1242   $257.12   $257.10   $257.10  
  7 purchase totals = $1,075.01       $1,174.6915   $1,174.69   $1,174.70   $1,174.60