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 $213.64   9.408%   $233.7393   $233.74   $233.75   $233.70  
  Purchase #2 $215.96   7.449%   $232.0469   $232.05   $232.05   $232.00  
  Purchase #3 $229.89   5.259%   $241.9799   $241.98   $242.00   $242.00  
  Purchase #4 $89.39   3.682%   $92.6813   $92.68   $92.70   $92.70  
  Purchase #5 $111.34   9.263%   $121.6534   $121.65   $121.65   $121.70  
  Purchase #6 $181.42   13.633%   $206.153   $206.15   $206.15   $206.20  
  Purchase #7 $28.30   13.130%   $32.0158   $32.02   $32.00   $32.00  
  7 purchase totals = $1,069.94       $1,160.2696   $1,160.27   $1,160.30   $1,160.30