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 $54.80   10.602%   $60.6099   $60.61   $60.60   $60.60  
  Purchase #2 $32.37   10.486%   $35.7643   $35.76   $35.75   $35.80  
  Purchase #3 $216.50   13.846%   $246.4766   $246.48   $246.50   $246.50  
  Purchase #4 $55.46   11.221%   $61.6832   $61.68   $61.70   $61.70  
  Purchase #5 $107.97   7.852%   $116.4478   $116.45   $116.45   $116.40  
  Purchase #6 $113.41   10.241%   $125.0243   $125.02   $125.00   $125.00  
  Purchase #7 $106.28   13.200%   $120.309   $120.31   $120.30   $120.30  
  7 purchase totals = $686.79       $766.3151   $766.31   $766.30   $766.30