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 $92.74   4.249%   $96.6805   $96.68   $96.70   $96.70  
  Purchase #2 $213.35   9.514%   $233.6481   $233.65   $233.65   $233.60  
  Purchase #3 $33.77   10.170%   $37.2044   $37.20   $37.20   $37.20  
  Purchase #4 $144.98   11.721%   $161.9731   $161.97   $161.95   $162.00  
  Purchase #5 $162.34   7.128%   $173.9116   $173.91   $173.90   $173.90  
  Purchase #6 $212.99   4.380%   $222.319   $222.32   $222.30   $222.30  
  Purchase #7 $151.76   10.168%   $167.191   $167.19   $167.20   $167.20  
  7 purchase totals = $1,011.93       $1,092.9277   $1,092.92   $1,092.90   $1,092.90