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 $62.54   3.215%   $64.5507   $64.55   $64.55   $64.60  
  Purchase #2 $197.29   10.838%   $218.6723   $218.67   $218.65   $218.70  
  Purchase #3 $136.54   4.429%   $142.5874   $142.59   $142.60   $142.60  
  Purchase #4 $121.71   10.376%   $134.3386   $134.34   $134.35   $134.30  
  Purchase #5 $223.55   4.134%   $232.7916   $232.79   $232.80   $232.80  
  Purchase #6 $183.28   5.171%   $192.7574   $192.76   $192.75   $192.80  
  Purchase #7 $209.84   6.172%   $222.7913   $222.79   $222.80   $222.80  
  7 purchase totals = $1,134.75       $1,208.4893   $1,208.49   $1,208.50   $1,208.60