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 $44.95   3.558%   $46.5493   $46.55   $46.55   $46.50  
  Purchase #2 $198.93   11.585%   $221.976   $221.98   $222.00   $222.00  
  Purchase #3 $230.28   13.858%   $262.1922   $262.19   $262.20   $262.20  
  Purchase #4 $201.52   6.797%   $215.2173   $215.22   $215.20   $215.20  
  Purchase #5 $167.72   11.826%   $187.5546   $187.55   $187.55   $187.60  
  Purchase #6 $117.49   6.854%   $125.5428   $125.54   $125.55   $125.50  
  Purchase #7 $59.98   13.568%   $68.1181   $68.12   $68.10   $68.10  
  7 purchase totals = $1,020.87       $1,127.1503   $1,127.15   $1,127.15   $1,127.10