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 $65.62   5.242%   $69.0598   $69.06   $69.05   $69.10  
  Purchase #2 $207.69   9.309%   $227.0239   $227.02   $227.00   $227.00  
  Purchase #3 $208.35   5.862%   $220.5635   $220.56   $220.55   $220.60  
  Purchase #4 $147.85   12.467%   $166.2825   $166.28   $166.30   $166.30  
  Purchase #5 $132.34   12.868%   $149.3695   $149.37   $149.35   $149.40  
  Purchase #6 $147.30   6.825%   $157.3532   $157.35   $157.35   $157.40  
  Purchase #7 $120.38   9.756%   $132.1243   $132.12   $132.10   $132.10  
  7 purchase totals = $1,029.53       $1,121.7767   $1,121.76   $1,121.70   $1,121.90