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 $204.89   9.342%   $224.0308   $224.03   $224.05   $224.00  
  Purchase #2 $184.87   5.492%   $195.0231   $195.02   $195.00   $195.00  
  Purchase #3 $154.67   9.118%   $168.7728   $168.77   $168.75   $168.80  
  Purchase #4 $130.43   12.735%   $147.0403   $147.04   $147.05   $147.00  
  Purchase #5 $114.32   10.502%   $126.3259   $126.33   $126.35   $126.30  
  Purchase #6 $213.42   6.207%   $226.667   $226.67   $226.65   $226.70  
  Purchase #7 $16.58   7.439%   $17.8134   $17.81   $17.80   $17.80  
  7 purchase totals = $1,019.18       $1,105.6733   $1,105.67   $1,105.65   $1,105.60