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 $62.26   3.318%   $64.3258   $64.33   $64.35   $64.30  
  Purchase #2 $152.89   6.571%   $162.9364   $162.94   $162.95   $162.90  
  Purchase #3 $230.26   6.393%   $244.9805   $244.98   $245.00   $245.00  
  Purchase #4 $111.80   8.696%   $121.5221   $121.52   $121.50   $121.50  
  Purchase #5 $163.97   5.783%   $173.4524   $173.45   $173.45   $173.50  
  Purchase #6 $244.36   11.759%   $273.0943   $273.09   $273.10   $273.10  
  Purchase #7 $86.77   7.682%   $93.4357   $93.44   $93.45   $93.40  
  7 purchase totals = $1,052.31       $1,133.7472   $1,133.75   $1,133.80   $1,133.70