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 $238.45   11.204%   $265.1659   $265.17   $265.15   $265.20  
  Purchase #2 $167.26   5.227%   $176.0027   $176.00   $176.00   $176.00  
  Purchase #3 $201.53   11.500%   $224.706   $224.71   $224.70   $224.70  
  Purchase #4 $223.77   12.747%   $252.294   $252.29   $252.30   $252.30  
  Purchase #5 $112.88   6.408%   $120.1134   $120.11   $120.10   $120.10  
  Purchase #6 $131.94   10.297%   $145.5259   $145.53   $145.55   $145.50  
  Purchase #7 $28.92   5.455%   $30.4976   $30.50   $30.50   $30.50  
  7 purchase totals = $1,104.75       $1,214.3055   $1,214.31   $1,214.30   $1,214.30