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 $198.97   5.822%   $210.554   $210.55   $210.55   $210.60  
  Purchase #2 $209.95   12.704%   $236.622   $236.62   $236.60   $236.60  
  Purchase #3 $85.65   9.346%   $93.6548   $93.65   $93.65   $93.70  
  Purchase #4 $50.58   5.221%   $53.2208   $53.22   $53.20   $53.20  
  Purchase #5 $218.84   3.591%   $226.6985   $226.70   $226.70   $226.70  
  Purchase #6 $136.29   5.129%   $143.2803   $143.28   $143.30   $143.30  
  Purchase #7 $220.97   4.691%   $231.3357   $231.34   $231.35   $231.30  
  7 purchase totals = $1,121.25       $1,195.3661   $1,195.36   $1,195.35   $1,195.40