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 $237.77   11.430%   $264.9471   $264.95   $264.95   $264.90  
  Purchase #2 $165.36   3.254%   $170.7408   $170.74   $170.75   $170.70  
  Purchase #3 $159.53   3.533%   $165.1662   $165.17   $165.15   $165.20  
  Purchase #4 $187.26   9.296%   $204.6677   $204.67   $204.65   $204.70  
  Purchase #5 $44.46   11.559%   $49.5991   $49.60   $49.60   $49.60  
  Purchase #6 $190.60   12.111%   $213.6836   $213.68   $213.70   $213.70  
  Purchase #7 $121.82   3.813%   $126.465   $126.47   $126.45   $126.50  
  7 purchase totals = $1,106.80       $1,195.2695   $1,195.28   $1,195.25   $1,195.30