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 $59.39   3.279%   $61.3374   $61.34   $61.35   $61.30  
  Purchase #2 $228.43   8.478%   $247.7963   $247.80   $247.80   $247.80  
  Purchase #3 $219.61   7.460%   $235.9929   $235.99   $236.00   $236.00  
  Purchase #4 $37.26   3.622%   $38.6096   $38.61   $38.60   $38.60  
  Purchase #5 $177.71   5.408%   $187.3206   $187.32   $187.30   $187.30  
  Purchase #6 $163.89   7.663%   $176.4489   $176.45   $176.45   $176.40  
  Purchase #7 $176.42   3.646%   $182.8523   $182.85   $182.85   $182.90  
  7 purchase totals = $1,062.71       $1,130.3580   $1,130.36   $1,130.35   $1,130.30