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 $60.81   10.156%   $66.9859   $66.99   $67.00   $67.00  
  Purchase #2 $244.76   7.193%   $262.3656   $262.37   $262.35   $262.40  
  Purchase #3 $85.96   10.760%   $95.2093   $95.21   $95.20   $95.20  
  Purchase #4 $191.64   9.166%   $209.2057   $209.21   $209.20   $209.20  
  Purchase #5 $192.25   5.160%   $202.1701   $202.17   $202.15   $202.20  
  Purchase #6 $153.29   9.711%   $168.176   $168.18   $168.20   $168.20  
  Purchase #7 $185.28   6.505%   $197.3325   $197.33   $197.35   $197.30  
  7 purchase totals = $1,113.99       $1,201.4451   $1,201.46   $1,201.45   $1,201.50